@kumachan_0201 for kenta, I think it's probably rivalry, he felt left out by two of his best friends (childhood)
They are all already working while he is in school, it felt like they have a headstart more than him and he is lagging behind (maybe kinda that feeling when your friends get jobs first after graduating, while you are still doing job hunting, there is that pressure). And since he can't go pro because of his injury, I think what
@roseofquartz said is correct, he probably gave up on school because he gave up on baseball.
I feel like in japan, there are people who went into professional industry after middle school or high school, either they learn how to become sushi chefs, etc. In this story sumire went and became a maiko, and then when she reach adulthood she will become geiko. Tho it is a very different culture than I have in my life, like not having backups, only have 1 thing to pursue as a career for your whole life, that kinda felt like scary... But then the culture is different in Japan