Guys, this game IS netorare, at the beginning it's not since MC and Girl weren't in a relationship, but after MC finds out her story, they start dating for months, at certain point the President says that MC is being deceived and invited him to a 'night school festival' (the name of this game) where he discovers that her GF was indeed still cheating him with so many people.
At the very end, he accepts this. Months(years?) later, we can discover that their relationship is now a cuckold fantasy where the is the Manager of the swimming club and let's his GF to fuck whoever she wants and enjoys.
All school knows this now haha even a small CG where President gives blowjobs to MC, and it's implicit that MC is having sex with the nurse too.
So it's a win win situation for both.