A little history first; According to recorded history, which is of course wrong, the previous person to be summoned turned into the Demon King and wreaked havoc on the world. It's due to this that when Camilla Resenburg summons from Japan, she tries to tone it down by summoning a group of individuals instead of just one, in an attempt to tone down the power and make it less likely for them to be a Demon King. As for the treatment afterwards, imagine you're summoning 300+ potential criminals, of course you would use whatever means you have at hand to keep them under control so they won't cause trouble, in this case it happens to be modified s*ave bracelets. She tells her knights to treat specific people as examples, the banishing of the MC who was misjudged by the 'Evil Eye Crystal', and the treatment of the most hated person in class, Funayama. Although the knights take it too far and Funayama winds up dying as a result. Almost all the evils done to them were done because of un-knightly knights who later get punished. Sure Camilla gave them the original orders, but if you're the warden of a prison, you don't really care how the prisoners are treated. She later comes to learn that she was wrong and people summoned from Japan aren't evil/potential Demon Kings and tries to make it right, but at the time she had too much on her hands to care about the treatment of criminals.

fear of abandonment caused by parental neglect

he is equally proficient in opposing attributes so they cancel each other out as far as the measurement tool is concerned.

The entire third floor of a school is transported to another world, causing the fourth floor to collapse onto the lower floors, resulting in injury and death for those caught up in the event.

One example is when he's negotiating with the Emperor of Barshania to allow Japanese survey teams to check for resources. The Emperor reminds him that he, as Emperor, can negotiate for his nation, but can Kento say the same? As he realises he can't he gets a ton of life advice, which he gladly accepts.

Another one is when Donovan and Klaus admonish him for babying his classmates. They're considered to be adults so why does he want to apologise for their s*upidity? He managed to survive in the city on his own, asking for advice when needed, so why does he take responsibility for them? Especially after they were told that Volzad is accomodating them mostly because of his accomplishments. He accepts that they're right, though he still wants to help them.

Yes, I'm talking about Yagi. He does get better after a flat chested beastwoman makes him her husband, due to circumstances caused entirely by him, but remains mostly the same.

Manon is a tomboyish girl next door, who shared shared some good and bad times with Kento, and is experiencing her first love. Beatrice and Seraphina are daughters of politicians and understand his immense strategic value. Yuika (the Chairman) started with a suspension bridge effect because he was her only source of comfort when she was ens*aved. Camilla? Really looks like Stockholm Syndrome, he almost terrified her out of her mind when she though she summoned a Demon Lord. And then proceeeded to treat her like crap, which she deserved, while actually accomplishing the goals she set for herself. Incidentally her character development (she's not evil, just terribly misguided), redemption and their romance are one of the longest running arcs in the novel. It culminates with them doing the deed and her being accepted as his soon-to-be wife, but it takes over 500 chapters.

Of course all of them genuinely end up loving Kento pretty fast, but their initial interest in him happens for believable reasons.

Well the first 150 chapter is excellent. The pace is quite balance, not too fast nor too slow. It's about the rescue his classmate. It's also including the problem of harem. As of c502, MC has 4 wives officially and 1 to be wives soon.

The first three is quite fast to achieved. The fourth is taking a long time to time, not to mention the fifth. It's a bit of drama with the fifth.

After being rescued, the story is go downhill. I'm not saying it's bad. It's more like from excellent to good. Since it's more about how to return to original world, the consequences, and the psychology being isekai. It's become drama oriented. This is also the start where MC truly start exploring the isekai world.

This is where it becomes hectic, it's jumble the story. Problems keeps popping up one after the other, not just on MC but also on side characters too that choose to stay in the isekai world since they've been flashed out more in c400 onwards, especially Yagi, the glasses classmate. There's Meri (female character that's introduced around c420) that adores Honmiya (a girl classmate that choose to stay). There's indication of yuri. There's also a romantic interest of other side charater that died and reincarnated as a child. The more story progress, there's a lot of question that need to be answer. There's no clear main villain yet, there's also no god that fit in the story even though there's a church.

So I'll just wait until the novel is complete.

As of c502, MC has 4 wives and 1 soon to be

Yuika (the Saint, class rep, Japanese person, also an insider for rescue operation, that's why she also has a lot of interactions with MC)

Manon (ordinary Volzard girl, has a lot interactions with MC after he's arrive in Volzard)

Beatrice (Volzard lord 2nd daughter, being saved from dying because a disease),

Serafima (princess of Balsahnia, peeping her while she's asleep, and according to tradition she needs to marry those who sees her sleeping figure. The guards is ridiculous strict though, but MC is OP, and Serafime is the brain in royalty.)

and the soon to be is Camilla (princess of Resenburg, the one who summon MC and his classmate, she's not exactly a villain at first, also she almost died 2 times and almost r*ped 1 times, basically she's a good person but her surrounding is just worst, that's why she's appeared villainy at first).

There's some girls that aim the MC, well actually there's a lot, but this is with highest possibility and interesting in my opinion:

Meisa (the daugther of his boarding house, she truly loves MC, but MC think of her like little sister, because she's just 10 years old and have 0 s*x appeal. Her dreams is to be MC bride.)

Watanuki (MC classmate, her past is dark, she's been r*ped by 3 knights for 2 months before finally being rescued, become desperate, hence she's become s**tty after being rescued. She has relationship with few classmates and have s*x with them and become pregnant. She's been helped a lot by MC, financially, mentally, it's almost like a husband. MC is also willing to do anything for her, like hit the boy who abandoned her after he knows that she's pregnant, comforting her cry after being abandoned, doing cruel things to those 3 knights, even killing them, if Watanuki wants it, those 3 knights is beheaded though by Camilla knights, extort compensation from Resenburg for her, and so on. She actually want to be MC wives, but even if she's being chosen, she's believe it's not 100% love, but half of it is pity. She also decide that she's can't choose any other man than MC until she can be proud of herself)

conquers Reisenburg, and faces his arch-nemesis mano a mano.

Even if they're s*aves, they won't be motivated to become strong and help her if she treats them and their friends so poorly. Actually, she treats everyone else I've seen her interact with poorly but somehow still has a great reputation... Also, the existence of mass-produced items that can allow anyone to control people just by putting it on the victim's wrist is both scary and unrealistic. If you can summon powerful humans from other worlds and create ens*avement items, can't you put that effort into solving your problems in other ways?

MC works his ass off for people who he wants to help, but often are ungrateful, lazy, entitled, whiners. This seems sweet but its demented because he doesn't even realize how desperate he is for acceptance and approval. The main princess b*tch-face, scowler of scowlers, down-nose looker of down-lookers, deserver of razor enemas, is somehow... a good girl now?