This is not a revenge story. That's important to mention because it very easily could have been – like the protagonists of other similarly set-up titles, Yuuya is at the absolute bottom of the world's hierarchy when he stumbles into amazing powers that rewrite his life, and it would have been very, very easy for him to succumb to his anger and reinvent himself as the most amazing human being to ever exist, taking down those who abandoned him with impunity. But that's not what Yuuya does, and for one very simple (and good) reason: he's been put down for so long that he doesn't believe that he's worth anything.

Prior to discovering the portal that leads to his powering up, Yuuya spent his life being treated like garbage. An overweight and unattractive child, he grew into a teen of the same description, and his parents quickly wrote him off once his younger twin siblings were born, essentially reducing him to an Ash Lad (male Cinderella). He ate scraps, wore clothes until they were rags, and basically was forced to doubt his own right to exist. The one ray of light in all of this was his grandfather, who did his best during his infrequent returns to Japan from his international (and possibly interdimensional) travels. When he died, he left everything to Yuuya, so he was at least able to move out of the family home and into his grandfather's house. This did nothing to improve the way anyone treated him, however, and even teachers joined the students at school in tormenting him. Yuuya was the easiest of targets because he never fought back, having internalized his family's belief that he didn't have the right to exist.

Some of these things begin to change, however, when he discovers a mysterious door while cleaning his grandfather's house. The door leads him to another world, where he gains the inevitable game menu and stats. The power-ups he receives from this rewrite his body on the cellular level in addition to giving him strengths and skills that carry over into the real world. Any other light novel hero would be sitting pretty at this point, happily proving that he's nobody's punching bag anymore, but Yuuya's PTSD is treated with rather more fidelity. He can't become that person because he still sees himself as the overweight and unloved boy he's been his entire life. As some of his new friends note, the only person who doesn't believe in him at this point is himself.

That's not to say that no vengeance is wreaked, but it's largely a side product of Yuuya just being a decent human being. And in fact the very first rescue he effects happens when he hasn't been turned into a hot and fit god yet – when he sees thugs harassing Kaori, another high schooler, he steps up to save her by distracting their attention. His behavior immediately wins Kaori over, and when she meets him for the second time, newly attractive, his improved physique barely even registers: she likes him and wants to help him because he helped her and is a good person. If his outsides now match his insides, that's largely a big whatever to her. The implication that the other students and the wonderful new school she invites him to (her dad's the principal) also see him for who he is and not just what he looks like is pretty strong as well; most of his interactions with them focus more on them liking him as a person not just wanting to talk to him because he's gorgeous.

His new looks do play a role in his life, of course, but interestingly enough that's presented as more of a negative than anything, and the real-world villain (once his former bullies are disposed of) is someone who wants to take advantage of his looks to make her modeling agency more money. The fact that his bullies don't care that he's strong and handsome now supports the idea that it's less about looks than actions and personality as well, because his new appearance certainly doesn't stop them from coming after him (and Kaori) until he forces them to. Naturally there are three (at least) lovely ladies who all are interested in him – two in the real world and one in the fantasy realm – but right now he's too down on himself to believe that they mean it. Kaori, the only one to see him both before and after, seems to stand above the other two because we know that her interest in him is more than just based on his new strength and good looks.

I Got a Cheat Skill in Another World and Became Unrivaled in The Real World, Too may not continue in this vein as it goes on. That would be a shame, because the throughline of Yuuya having to learn to trust and like himself is a solid one and it really does set the book apart from other similar novels. It isn't entirely free of the usual genre trappings and the art is a little unsettling with how far apart the eyes are set on the faces, but it's also a generally good read that spends as much time in the modern world as it does in the isekai realm. If you're looking for a story that's more than just cheap revenge, this is worth checking out.