Dude, her ex is a total douchebag. You don't just use people to figure out your sexual orientation. Just because you're gay doesn't mean you can use people and get away with it without even apologizing.
Basically a manga about the worst type of fujoshi's wet dream. Fetishization of gay men, dumb horny MC, cheating ML. This manga is a dumpster filled with used condoms. Even reading yuri vanilla hentai would've been better. This manga made me lesbian.