Go read the prequel to this called challengers. It's shown there.
it’s a mix of a few things like the assistant professor attempting to assault him, thinking a gay man (tomoe’s now bf) was manipulating/using his younger ditzy brother, and probably/implied internalized homophobia
Kurokawa is his husband! There was also Phil who was gay and hitting on Tomoe and Souichi decided Kurokawa was safer then Phil lol...
But the main reason was his professor tried to rape him and Morinaga saved him.
yes thank you! i lowkey forgot because them getting married was a kinda gag way back at the very beginning of koisuru lol and i basically sped thru challengers
But then Moinaga raped him… So messy in the beginning!!
Maybe it's been so long that I forgot the reason for senpai's hatred for gays , i remembering hearing the reason being him assaulted or smth just want some1 to clarify this claim