This is one of those stories where if we weren't purposely going for the slightly taboo rom-com story, the best answer would be for Gen to end up with the high school girl his age and her older relative to end up with the seemingly very nice older teacher her age who is happy to take up the temple business.
I don't really have a personal preference as it's fictional and the ending seems like a foregone conclusion, so why bother worrying about it, but it's just very noticeable here.