@kronix I thought about what you said and I'm thinking, that "limiting" himself to older women makes a lot of sense. Outside of the ethical issues, a DTF career woman with a job that you can go smoking and drinking with is automatically more appealing than a high school girl. MC says he hasn't grown emotionally since he was 16-- maybe hanging out with "older" people from the previous generation can bring some new flavor or maturity to his life. The office ladies, his sister and her boyfriend-- the only people he's met up with that have provoked some positive change in him have all been "older." I think it would be cool if he used his youth to learn how to live from other adults. And at this point, I think getting hung up on the high school stuff just reinforces his arrested development. He places the karate girl on a pedestal and he hasn't manned up to the point where he can maintain a relationship with his ex-wife now classmate.
Not to keep going back to the high school thing, but I'm in my 20s and high schoolers seem like children to me. The desirability of JK girls is kind of a trope in anime/manga, but when I think about a 60 year old man (or however old he is) being that emotionally/romantically invested in what should be basically toddlers from his perspective, that's suuuuuper odd and kind of sad. I think he should be dating up in age for his own emotional wellbeing. It seems like the longevity of a relationship is important to him and I don't know what he's going to get out of a long term relationship with a high school girl when he already knows their future and is already an old man.