? This is just my opinion, but i don’t think people just "turn" gay or bi. It’s more like they realize their true sexuality over time, or their attractions shift. even if a guy dated a woman before and turns out to be fully gay later, it's not "turning gay", it's just him discovering himself after trying to fit into societal norms
but if he still likes both, then he’s bi, right? Which brings me back to my exact point, the story could just acknowledge them as bisexual instead of framing it as "straight turned gay" like being bi doesn't exist

It’s pretty rare for me to find a manhwa that actually uses the term 'bisexual.' i mean likeee, it's not that rare to see a guy character date a girl and then a guy, but they usually just call it 'a straight man turning gay' instead of acknowledging he's bi