Honestly, the way the relationship developed between the two girls in this series is pretty shallow and even started off as r*pey... It didn't feel like a traditional Yuri where two girls naturally started developing feelings for each other gradually overtime. Instead, it felt more like a Stockholm syndrome situation. Our main protagonist (Marika) is a straight female and essentially she made a bet/contract with another girl (Aya). Because of this bet/contract, Marika can't really go against Aya's demands (partly due to pride) so she ends up in a lot of somewhat forceful s*xual situations. The love between Marika and Aya didn't feel natural but instead artificially created due to situational circumstances. I also don't really like how their relationship seems to be fueled more by carnal desire rather than actual affection (60% - 40%). Speaking of which, I think it's really s*upid how not even two weeks after making the bet/contract, the two girls already reached third base... For someone like Marika who's supposed to be a straight female and is adamant about her sexuality/preferences, she let herself get taken advantage of sexually pretty damn easily. I love adult scenes and what not but I don't like them when they're rushed and don't feel real.

As a side note, at times when they're talking about lesbian relationships, it kinda sounds like a toned down LGBT propaganda (the ones where they try to project their opinions/beliefs onto others).

It turns out that the sharp gaze is coming from our class' cool beauty, Fuwa Aya.

Seeing her delicate appearance, you’d think she could do no wrong. Her aura and her eyes make her look sleepy at all times, and that, combined with the sensual air that surrounds her and her gorgeous appearance, make it hard to approach her. It's the reason why she’s a lone wolf in this class.

A nicely shaped nose, soft beautiful hair that flows without any signs of bed head. Her glowing skin makes me wonder what kind of UV care she uses. From the top of her hair to the tips of her toes, each part is so beautiful that I’d believe she was crafted from porcelain. She stands at around 160 cm, she has a great style and emits an elegant air wherever she goes. I’ve seen her get invited by a couple of our school's sports clubs, but she ended up in the going-home club.

A hand, white like porcelain, got closer and touched my ears lightly. My body reacted on its own by jolting.

She looks even more stunning than she does in school. She has on a simple eye shadow that emphasizes the shape of her eyes. For her clothes, she chose a sleeveless blouse paired with a tight skirt to emphasize her figure. She’s wearing 7-cm heels that synergize well with her handbag. Her appearance tonight closely resembles my mental image of a ‘Lady of the Night’.

She suddenly appeared, wearing a white shirt that was covered with a coat. She also wore a tie and long black trousers. Her long hair is neatly tied into a ponytail. If I didn’t know she was Fuwa Aya, I may have fallen in love at first sight, simply because she was so captivating.

She is an EXTREME tsundere, she always does things that she doesn't need to comfort and show affecting towards the love interest, she is literally the stereotype that compliments all the time the love interest and then says or think of some mental gymnastic like "it's a neutral and universal opinion ok?", "but it's not I like you or anything ok?".

From the very beginning she does stuff she doesn't needed, the love interest kisses her and she kisses back PASSIONATELY " All I can remember is that I got so desperate that I ended up kissing Fuwa with all my might"

She gets dead jealousy about her, at the bar she started to get more intimate to her by calling her the first name like the other, but the others were doing it because it was her professional name and had a tag in the clothes. She knowing her real name and it's described as a murky feeling that went away after seeing the love interest reaction, another huge hint of it is her outburst of rage in the bathroom because she thought that she looked too experienced doing stuff, and thinking that she might have slept with more woman she lost it because of jelousy.

Basically they have a bet and a contract with money to see if the MC will fall in love with the love interest, but the MC pretty much always had feelings for her from what we see from the very beginning, she competed with her inside her head and never stopped to think about her on any social aspect, anyway, the MC agreed on EVERYTHING le*d related because that's what they agreed on, for 100 days she will sell her body to her, BUT she is also a tsundere and doesn't/can't show that she likes her because she'll lose that bet/contract, so whenever the love interest is doing anything to her, and she is showing any sign of pleasure and gets called out, the MC denies it and says she is lying, but on the other hand she never refuses, complains or thinks it's a bad thing

further more, when they don't go all the way, she gets frustrated and A LOT here's examples (the first one is good to show her mental gymnastic to try to convince herself she isn't into her) :

After a while, Fuwa pulled her head back and looked down at me. Nobody said anything for a brief moment, all I could hear was the sound of our breathing echoing inside this room. Then, Fuwa smiled.

"Okay that's it."

".... Huh?"

"Just one thing, I wanted her to understand that right now, I’m longing for a physical bond, it’s not like I’m longing for a girl or something like that. I want her to properly understand that what she did only made me sexually frustrated, that it didn’t have anything to do with gender or sexuality."

and what would look more forceful is:

"Eh? You know? And you are still doing this and that despite my feelings? I don't get it."

"It excites me to know that my target dislikes me. It really lights my fire."

Now if I find something that IS indeed r*pe I'll edit and update it but for now it's just interpretation from people.

Vol 1 = The part where Aya wants to make Marika to be her girlfriend (this volume is filled with forced s*x etc.) But in the end of the story, Aya tells her true reason about why she made a contract with Marika.

Vol 2 = They started dating and begins to accept each other. This volume is basically sweeter than the first volume. You can start reading here if you don't really care about the reason why Aya and Marika are dating.

Vol 3 = I don't wanna spoil this, but basically it's a story between Aya and Marika where they live together for a week.