Responses
It's a very serious case of 'reality is unrealistic' even in fiction...most of the times people who are good at recognizing these things about others are the most clueless ones when feelings are directed at THEM.
It also helps that the ML was written to be a totally heterosexual harem master so ofc the MC would have serious troubles to even THINK he'd suddenly turn gay.
But that's what makes it so hilarious after all. It would be 100% less funny if he were to actually notice what was happening right away.

Ok Mc starting to be annoying, he was a CEO and playboy in his past life and he still can't tell that ML like him, like my dude everybody can tell.