That comment about breaking up quickly with girls and feeling comfortable around them sounds like hints towards gay rather than bi.
He’s gay but he’s into female presenting ones. Hmm. Much to consider
I think an editor stepped in and changed the course of the manga. Or the author themselves didn’t want it to go in that serious direction that they set it up to go. Look at their other works, it’s not really something they write.
But maybe they wanted to give it a try anyway and either didn’t...
I think a lot of people will make that choice. It’s not as lopsided as you think. However the problem is that zombies can’t consent so that’s why the author put that whole foreplay stuff in there so it doesn’t feel like rape. Even though it kind of is.