My Stepsister is My Ex


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A certain boy and girl in middle school became a couple, flirted with each other, disagreed on trivial things, became more frequently irritated with each other… and eventually broke up upon graduation.

Now in highschool, the two of them, Irido Mizuto and Ayai Yume, wound up meeting each other in the most unexpected fashion.

The former couple, brought together through parental remarriage, decided to be mindful of their parents’ feelings and came up with a ‘sibling rule’—where the the first one to become conscious of the other as a member of the other s*x loses, but…

When they encounter each other in the bathroom, commute to and from school together, along with the memories of the past and living under the same roof, just how do they disregard each other!?

Associated Names
One entry per line
Mamahaha no Tsurego ga Motokano datta
My Stepmom's Daughter Is My Ex
My Stepsister is My Ex-Girlfriend
Related Series
Gimai Seikatsu (11)
Otonari no Tenshi-sama ni Itsu no Ma ni ka Dame Ningen ni Sareteita Ken (LN) (1)
I’m Fine With Being the Second Girlfriend (1)
The Results From When I Time Leaped to My Second Year of High School and Confessed to the Teacher I Liked at the Time (WN) (1)
The Neighboring Aarya-san who Sometimes Acts Affectionate and Murmuring in Russian (1)
The Neat and Pretty Girl at My New School Is a Childhood Friend of Mine Who I Thought Was a Boy (WN) (1)
Recommendation Lists
  1. Best List
  2. NaCl's read list
  3. Beloved Tsunderes
  4. Dropped
  5. School Life

Latest Release

Date Group Release
11/24/23 Glucose Translations v10.5c1 part2
11/20/23 Glucose Translations v10.5c1 part1
06/19/23 Glucose Translations v10c5
05/30/23 Glucose Translations v10c4
05/23/23 Glucose Translations v10c3
05/04/23 Glucose Translations v10c2
04/12/23 Glucose Translations v10c1
04/07/23 Glucose Translations v10 illustrations
09/29/22 Glucose Translations v9c6
09/29/22 Glucose Translations v9c5
09/29/22 Glucose Translations v9c4
09/29/22 Glucose Translations v9c3
09/29/22 Glucose Translations v9c2
09/29/22 Glucose Translations v9c1
09/28/22 Glucose Translations v9 illustrations
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30 Reviews

New iseru
Nov 13, 2023
Status: v10c5
One of the best RomComs I've read.

The main characters – Mizuto and Yume Irido – are both likeable and together create a nice dynamic for the story. The novel alternate narrators between all the characters, which is quite unique and enjoyable to be able to understand their inner thoughts. While it's a bit slow paced at first with a lot of 'resets' in each volume, I enjoyed the gradual progression and it was never boring anyways. Besides, everything does come together in the end, so it's important to be patient!... more>> In the later volumes, we're introduced to side characters with their own romantic relationships as side stories. Each of the characters had their own idiosyncrasies that defined their persona, seeing their stories progress in the later volumes was just as enjoyable as the main plot of the Iridos.

10/10 for me, if you're into fluffy RomComs with a certain degree of depth, definitely give it a go. <<less
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Aug 11, 2021
Status: v7 afterword
Perhaps it would be boring if readers are only looking for romantic progression and ignore every single character development in the story, like some others would have insinuated anywhere and not justify so?

Do we also ignore how the main five evolve as people, instead of just reading the story for the sake of the faux-domekano plotline and hoping for a resolution without looking into the whats and the whys as to why the characters are as they are, and instead only nitpick because the romance isn't progressing as fast as... more>> they would like?

Do we also ignore how the main five look into their past and actually reflect on their actions, something that is blatantly missing in most other light novels out there, and also come to a positive conclusion on what they should improve on, even if the effort is for naught, and instead only nitpick because the romance isn't progressing as fast as they would like? Do we also only look at the superficial of the actions and complain that there isn't any progression because the only thing people look at nowadays is simply romance = progression?

Because 'My stepsister is my ex' isn't this kind of story.

Alright, admittedly, as noted by the author in the afterwords, this series was initially meant to be a love-hate relationship because the stepsiblings who were once a couple had to get used to living together. There are some romcom hijinxs here and there, but as you read further, you'll see more depth into each other's character, sometimes boring, sometimes scary, sometimes hilarious, but that's part and parcel of being human (aside from all the contrived coincidences involving four out of the five characters)

We have extroverts like Kogure, introverts trying to be extrovert (changing oneself) like Yume, introverts who'd rather remain the same like Mizuto. Not everything is about romance in this story, for they need to understand each other to get along better as ex-couples, and also as friends/siblings.

Bottom line, if you're just looking for a romantic resolution in this story, this story isn't for you because it looks into way more things than that, and most readers can't have that. This isn't like Otonari no Tenshi-sama when it gets sweet and then nothing else later on in the story. If you just want romance resolution, just read the author's other series 'Do you think you can run after reincarnating, nii-san?' <<less
37 Likes · Like Permalink | Report
Jan 27, 2022
Status: v7
I have to say that I have mixed feelings on it. On one hand it does some things great, between interesting characters and several genuinely touching chapters (The Dancing Girl of Siberia for example). The writing and translation is on point and overall it’s a rather excellent story.

There are two big detractors from me giving it 5*.

The first is the waffling about. They’re stuck in this constant game of “will they, won’t they” where progress is immediately abandoned as if events never happened. Volume 1 was honestly worthy of 5*... more>> to me, and each volume when taken by itself would probably be the same, but the author half resets the relationship in between each volume in order to basically pad the series out. There is overall progress, but it kinda feels like they’re barely closer than they were at the end of V1 even now at the end of V7 (though with how this one ended I hope there’s no more of these resets).

The other is frankly unnecessary characters added to further the drama. I’m talking about one in particular. The male lead in the later volumes has several moments that made me immensely dislike his actions, and it’s just excused because he basically is mentally challenged in regards to forming relationships.

In volume 7 his best friend is another socially challenged girl and she breaks her bra and has him hide it, meanwhile the female lead tries to talk to him later that day but he runs away. Hiding stuff like that, even if it’s not easy to explain, leaves me with an awful impression of him. This whole scene caused drama too, which was annoying. That’s not even mentioning how that ‘best friend’ is constantly trying to seduce him despite being friends with the actual female lead character who is basically in a relationship with him at this point. Just feels super scummy.


I feel like these issues are present because this story is in a weird spot where it’s mostly a serious romance/drama but with quirky characters and comedic moments slipped in. <<less
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Sep 29, 2021
Status: --
First volume was very good, but like others stated, story gets a little boring when author focuses on the other couple with strange personal traits. I just couldn't force myself to be interested in them. And they were obstructing story constantly.

If it comes to main couple, FMC cannot decide what she wants and when she makes a little progress in one direction she immediately retracts two steps back, over and over. MC on the other side doesn't seem to be even interested in romance.

My main complain however are illustrations, they... more>> are high quality but age-wise I would place them in early middle school rather than high school, which is quite disturbing when comparing to their adult-like actions. <<less
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Aug 19, 2021
Status: v7 afterword
First and foremost, this is a fun read. There are decent character developments. The interactions are good and conversations feel natural. But just as the other review points out, it gets repetitive fast. To be honest, repetition itself is not bad but it makes me confused about what the author actually wants to convey here. This series started out very good and has an intriguing setting. But after that, the series returns to a typical slice-of-life LN where it focuses on the daily interactions of MC and FMC with others... more>> (rather than between themselves).

Personally, I find the series' focus on other couples/love interests annoying. Not that they are bad, but I am here to find out how the MC and FMC will grow their relationship. I want to see more of their mutual interactions without the heavy dependence on side characters. According to my humble estimation, 70 to 80% of each volume, after vol 4, start to deliberately explain the side love interests while an audience like me is rewarded with a short, swift, and sweet moment of MC-FMC at the very end of the volume and that's it.

At volume 7, I am completely lost as I cannot catch up with the introduction of so many characters, each with their own personalities and stories. Each of them conveys different messages and/or influences toward the FMC. In the end, it becomes a mess. Maybe I'm a bad reader and that's on me, but when so much focuses are dedicated to these side characters, you will also start to question the direction the author wants to take. <<less
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Aug 10, 2021
Status: v7 afterwards
Gets repetitive after the female MC realises she likes the MC (who are step-siblings) :

    • Female lead: I must seduce MC and make him only think about me.
    • Then she asks her friends some dumb plans to seduce MC (like walking naked after bath).
    • Her plans fail because MC has poker face after seeing her naked.
    • Then Female lead complains her friend how their dumb plan failed.
    • MC spends 90% of time with another girl who is his best friend, they get along so well that they'd make perfect couple.
    • MC and his girl best friend having 10x times more plot development than main couple, but We all know she's just a plot device, MC is gonna still fall for his step-sister at the end anyway.
    • Then some school stuff happens, MC and his girl best friend spend more and more time together (90% of the time).
    • Female MC gets jealous, asks her friend for another dumb plan to seduce MC. Which fails.
    • At the last chapter of each volume - Female MC becomes damsel in distress (MENTAL SITUATION), MC and Female lead have some intimate conversation,
    • Now you you expect them to progress with their relationship but nope, In the next volume the female lead again comes up another dumb plan to seduce him.
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Aug 13, 2020
Status: v1c8
Very good. Sweet and fluffy story, it is basically a story where two middle school teenagers broke up because they didn't understand their partner and were sulking towards each others.

As they've been saying on their monologue, from that point onwards they could have gone separately without getting back or even communicate anymore, but because of plot they ended up as step-sibling and classmate on their new high school. This story is about their everyday lives, getting to understand the other personality much better than back then when they were still... more>> a couple, without any fake mask/personalities.

It is so obvious that both of them still hold each other as a very important partner, unconciously not letting the other to feel hurt; But since they are your typical teenagers, they are so stubborn with their own beliefs.. Trying so hard to convince themselves that they hate each other instead. I have a high expectation on this series. <<less
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Jan 15, 2023
Status: v9c6
I want to rate this higher, I do. I like the characters, I like their growth/progression and I like their history. It's just so frustratingly slow, like glacially slow.

It kind of feels like the author is treating this like an RPG, going through side quest after side quest after side quest before remembering about the main story that's going on, makes a little progress on that before deciding to jump face first back into side quests. Don't get me wrong, I'm not expecting or wanting things to be fast paced.... more>> I just dislike how it feels that despite events that should bring MC and FMC closer doesn't amount to much, if anything at all.

For example, back in volume 4 chapter 8

MC and FMC kiss

but afterward it's as though it didn't happen in the first place. At least for MC, anyways. FMC does make an effort and I think that makes things a bit more annoying.

It isn't until volume 9 that

MC finally gets over himself, makes a little effort and they start dating. But the whole situation when they finally do decide to start going out feels more like a business meeting than a heart-to-heart.


Just, ugh. I do like this title and I'll probably see it through til completion but I don't think it's nearly as good as it could be or that people are saying it is. <<less
9 Likes · Like Permalink | Report
Dec 12, 2022
Status: v7
Let's start with my with enjoyment rating.

Volume 1, 2, 4 - Great

Volume 3, 5, 6 - Mid

Volume 7 - Shit

It's seems everyone in this praise the Characters at this series, then this my description about them

    • MC - dude your ego is just too big. His kind protag that monologuing that he different from other ppl and didn't feel anything and then continue to complain about it. But DUDE! He never try to understand it!!
    • FMC - at early volume at she tried to do something, but after vol. 4, interaction between MC and FMC is just very low and then come vol. 7, FMC enter student council, interaction between MC and FMC only at first and last chapter of vol. 7
    • MC's BF - honestly I don't really hate her, but she know how FMC feel and she even said that she support FMC and MC, but what she did to suppurt them? Seduce MC of course.
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Rampage Debut
Rampage Debu
Jul 18, 2021
Status: v6 epilogue
This novel took me by surprise and in an extremely good way.

The main characters of this story are Mizuto Irido and Yume Ayai who became step siblings after their parents' remarriage. However, unlike normal siblings they harbor a secret, they were actually a couple almost an year before and only one month after their breakup, they find themselves tied in a relationship as siblings with their parents being unaware of their past relationship. How will this ex-couple respond to their new relationship?

Volume 1 is basically all fluffy romance (?) with... more>> each chapter switching to one of the step siblings' PoV, a feature that continues in all volumes. The first Volume is basically an introduction and it does its job well of conveying the past and present relationship of Mizuto and Yume.

However, it is the subsequent Volumes that really enrich the reading experience. From Volume 2, the story goes into indepth details of their past relationship, their thoughts, their views and what events led to their subsequent breakup. They learn more about each other as family, learn sides of each other which they had never seen before when they were dating and the misunderstandings and misconceptions they had about each other which led to their falling out. As they mature, their new experiences only reminds of how lightly they had taken their earlier relationship with a non-commital attitude.

And finally starting from Volume 4 onwards, they once again start to get close to each other with newer resolve to start their couple's relationship even better than before, now having known all they want to know about each other as family. It is precisely because they became step siblings that they can form even stronger bonds as couple. Volume 4 which is centered on Yume and Volume 6 which is centered on Mizuto's thoughts are my favorite volumes of this series so far. I never expected to having come across so much detail over their thoughts and course of actions in a story about step siblings. Simply amazing. <<less
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Dec 12, 2020
Status: v7 afterword
Thank heavens the MC has a functioning brain. In which, honestly is rare these days. The story is good and I love the character interactions.

First of all, the characters are all well-written out. Even if they're all relatively new ones, they all have their unique personalities. The author introduced them to us properly, giving more information about them. More or less, they were all going to play a role in the main couple since the MC and FMC's environment would be influenced by them as to how the main characters... more>> would act.

The story, it's rather slow but justified. Every volume is like a month that had passed, giving insights and important events as highlights of that month. For example, exams, summer, school festivals, and more. Each of those events would be where the story of each volume would revolve and would play a major role on it. Although one may think that some of the ideas are just re-used, what's not noticed much is the subtle difference in how our main characters would act and how they would think. The thing is, like what translator-san, aka Hell_ping stated, the main focus of the story is how our characters would improve as a person. We all learned that from volume 1 they truly hated one another (apparently they did cuz the author said so, but for me, it was a different case but oh well). As time goes on, the main characters would learn everything about the other in their day-to-day lives. So in a way, it's more of a slice-of-life series at this point but like already said before, well-written. The author leaves little foreshadowings every volume that becomes relevant for future volumes. That's how it always went. So if you weren't paying attention properly or reading briskly, you wouldn't notice them at all. That's what others fail to notice. One of the characters get unnecessary hate, wherein she was the one who actually did the most for the main characters is quite saddening. I'm talking about

Isana Higashira


Overall, an enjoyable series to read, and would highly recommend others to read so. I've had 10 people read this series and I only received positive feedbacks from them. It goes without saying for me, that it's truly worth 5*. <<less
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Apr 18, 2021
Status: v4c1
Pretty fun


Although i've read many series like this its always fun and fresh to read a new one and maintaning that sense of excitement is pretty good and I feel this way with this novel. The two mc's Yume and Mizuto are pretty much hardcore tsunderes they go the roundabout way of showing affection towards each other. Though its pretty obvious that they'll unite its still pretty fun reading it and also the side character are pretty interesting as well. Pretty good if you ask me I'm still looking forward... more>> to it <<less
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Aug 27, 2022
Status: --
Idk if it’s wrong to hate but Higashira is a character I can’t stand. I mean she tries to seduce the MC even after knowing the FL likes him and she is also a friend of FL and tries to use her innocence or obliviousness as an excuse for her actions.
5 Likes · Like Permalink | Report
Apr 09, 2021
Status: v4c1
This Kaguya-sama Love is a war meets stepsibling p*rn.

I hate myself for getting invested in this. The premise is so dumb, the title as well but then the damn characters are so well written you wouldn't expect it.

Two tsunderes trying to convince themselves they hate the other one. Three chapters in and you can read between the lines of what they actually love from each other. You never get to see their actual thoughts when they are being nice or concerned about the other.

So I leave with the piece of... more>> trivia that comes in ch 2 but it's basically the end of this series (even if its still a bit away)

Stepsiblings can get married to each other <<less
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Jun 05, 2020
Status: v1c2
Stepsibling romance. I'm aware stepsiblings are used so that it's "technically okay", but family is family.

Putting that aside, it's pretty typical for a romance novel.

They still love each other, they can't stop their feelings. By the second chapter, they already were about to kiss until their parents interrupted by coming home.

They fight, they blush, they insult each other while trying and failing to hide their feelings.
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Mar 25, 2022
Status: v8 afterword
As many of reviewers said, this is one of the better rom coms right now. More details will be mentioned below.

The main premise of the story is sorta dumb, but the story makes itself clear that the plot is very simplistic. It is what it is, and there are no plot twists or sudden revelation or anything. It's just the slow romance of two ex lovers, whose parents remarry and have to live with each other. They learn to overcome and accept each other's flaws, and slowly reconcile with each... more>> other.

The main cast's biggest obstacles are their own character flaws, each are unique and contribute hugely to the story as something they have to accept or overcome to reach their objectives. I love how the author makes the story's pace extremely slow so that they can spend time and build up their characters. It gives us insight to how they think, how they act and make us like them, makes them feel relatable and makes us root for them.

Character development is quite slow, but that is good, since we can clearly see how they slowly recognize their own flaws and learn to accept or to overcome that flaw. It is one of the elements in modern literature that is lacking, and I love this novel for that (unlike those self-insert cardboard characters from rom coms or Mary Sues/Gary Stus that have no substance whatsoever)

That said, I still have some complaints. Perhaps for me, the weakest point of this novel are volumes 7 and 8, when it suddenly introduces us to a wider cast of characters that are the student council members. The author uses the same slow pace to build up these characters too, which is an issue for me. The fact that they steal the spotlight from the 4 main characters, and the sudden and rapid change in perspectives between the original and new cast makes it quite frustrating to read.

I feel that instead of spending time to build up them in the main story, these characters can get their own spinoff instead. This is the main problem that makes Marvel Eternals such a terrible movie, where they introduce too many characters you kinda forget who is who. At least this one establishes who are the main characters and who are side characters. I still don't like how these side characters have too much spotlight on this arc, since they are still not as interesting as the main cast. And well, the main reason you come to this story is for the main cast, right?

Anyways, I'd rate this 4.5 out of 5. It could have been higher if not for the two latest volumes. <<less
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Jun 22, 2021
Status: v6 afterword
Surprisingly good story, much different from any other I've read. There was a lot of detours with a love triangel (not exactly) with a character I don't exactly like so it felt really long reading those part. But they're getting there, I suppose.

This is a very good read, highly recommended.
4 Likes · Like Permalink | Report
Sep 25, 2021
Status: v4 afterword
This story has good writing, interesting character interactions, and character development. The main couple is likable and cute. However, the pace is very slow. The first two volumes were great, but the story moves away from its focus on the main couple. Time is wasted on more and more side characters and the romance between the main couple progresses extremely slowly. It's a shame because I really do like the main couple and I want them to be happy, but I'm not going to wait another two years for them... more>> to finally admit their feelings to each other. I think this is the kind of series that you only want to read once it is already complete. Check this out again in a few years once the series is finished, I for one am going to do just that. <<less
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Mar 19, 2021
Status: v3 afterword
This is a beautiful work. Not only interesting and funny, but well written, and makes you think too. The past is double linked to the present, and makes you understand and see everything under a new light.
3 Likes · Like Permalink | Report
Jan 11, 2021
Status: v1c3
Very High Quality, both parties have a good mind and go through memory lane resolving past misunderstandings and learning to love each other again!
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Jun 28, 2022
Status: v8
This is incredibly good

This isn't like many other romcoms where the entire world revolves around the 2 protagonists and the others are just supporting characters with a little bit of background. New characters are introduced at the right pace and they're explored beyond a simple "I exist purely to comment and egg on the protagonists"

And the characters, oh the characters do they grow.

... more>> It's not like "I'm an antisocial who eventually got friends and became popular". No, not that kind of superficial growth.

"I'm a weak maiden who needs a strong man to support my fragile heart, but now I'm a strong independent woman who don't need no man". No, not that kind of growth either

It's not a fluffy sugary sweet feel good growth, but a real growth. They have a heart, they hate, they really do. They spit poison, they sabotage, but they eventually settled with that. But that didn't happen in the first volume. Oh no, not even in the second, or the third. Progress takes time, and they have all the time in the world.

Everything has a cause, and their hate has a cause. It takes a lot of effort, but eventually they discovered the cause, they denied it, but gradually accepted it, before eventually settling with it.

The mere thought of the other used to break out a barrage of insult, the result of hatred borne out of circumstances and lack of experience. All they could see out of the other is negative, like a blood tinted glasses: the only thing they remembered were bitter memories. But they grow as people, they learned about each other, they finally see what they never saw, and eventually the nightmares subside, and the happy memories started to surface. It feels good

It's not the sweet kind of good, it's not the fluffy kind of good

It's the kind of good that you feel once you've arrived at your destination, with sweat, blood, and tears as the bus fare. There was so much pain, but you can't help to break out a smile at the end

It's like watching a kid struggling with a problem, scratching their head, screaming in pain, until they finally found the solution and yelled with tremendous joy.

Right now there's no goal in sight. This isn't a brand new experience, we've been on this trip many times before, we can guess where our destination is. It's going to be nothing new

But that's okay, because this journey is still worth watching <<less
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