Welp, as someone who's straight but self-inserts as the sub in forced fem (femdom) situations, my expert judgement of this protagonist is that he obviously subconsciously was interested in gay sex, or he wouldn't have made the obvious dumb choices to lock on the chastity belt given to him by a woman who obviously arranged to let her husband bang him previously, then visit her house and let her tie him up, and only vaguely protest when he raped him and then grew to like it. He also would've taken a chance and confessed to the girl he claimed to have a crush in, if he was more interested in straight romance than having a man's dick in his butt.
But he threw away every chance he get, so yeah, there you have it. The girl in his class Rena actually did love him before, and thinking back to how her older sister had encouraged him to confess but he just blew it off, this guy never demonstrated any sincerity in relationships, did he? Just followed his lust selfishly. In any case, I applied the NTR tag (which includes BSS by definition here) since they had mutual crushes before Rena found a new boyfriend.
I do still hope he manages to hook up with someone, maybe another sub woman he can build a family with who'll be okay with him letting men fuck him since clearly that's very important to him. Far from the most depressing feminization story I've read, I'll say that much.