It's all start from the brief dammit. The curiosity after peeking nemu changing clothes and wanting to have some of that. Simple ┑(￣Д ￣)┍
Well, it's more or less given a light explanation in the dj "Imasara Briefs"-- apparently, there was a light interest and curiosity Maya had towards Nemu when he saw Nemu changing in the locker room for P.E.
Not to mention: a lot of these BL mangas have this "gay for you (and only you)" set up; sexuality by real world standards never really apply in BL unless the author intends it. Just take Yonezou sensei's other work Elektal Delusion as an example to that.
Actually, if i recall correctly, there was a prologue short chapter narrating why Maya did what he did in Chapter 1. But for the life of me, I can't remember where i read it (￣∇￣")
Ok. So I really love this manga despite the way it started out (blackmail- not a good start to a relationship), but what is still driving me crazy is Maya! We see Nemugasa slowly develop feelings for Maya, and we see that Maya is crazy about him, but we never see what brought this on for Maya! I mean what kinda popular hetrosexual cisgender teenager to wake up one day and decide- " I know what i'll do today! I will trick the nerdiest guy in my grade so that I can blackmail him into sleeping with me."?! It's not like he was lacking in willing female bed partners before. And from his reactions in other chapters it's safe to assume that Nemugasa is the only male he has, and ever will be, interested in; he does not seem to consider himself homosexual, or even really bisexual. So how did all this even start? When, how and why did Maya become interested in Nemugasa in the first place, seemingly out of the blue?! Explain Nekota Yonezou sensei! EXPLAIN! ┑(￣Д ￣)┍