So this is a yaoi/shounen ai. The (gay) MC is transmigrated into an interstellar novel where there are no gays and he becomes a talented youth with a sunny personality. The first meeting between him and the (straight) ML is during a magic aptitude test where the MC and ML start their rivalry due to their good scores. They become friends quickly and share a dorm room. At one point the MC and his group of friends (including ML) get kidnapped by space pirates, during this time the MC persuades the pirates and gains a bit of time for himself and his friends, during this the ML switches back to his pirate persona while no one's paying attention and slaughters the entire pirate crew, he collects some flowers that were in the botany room of the ship and leaves them for the MC which provokes him, I think he takes it as a challenge to his um... Gayness? Or maybe his dominance? Idk I haven't read it in a while . Anyway, this situation where the ML provokes the MC's feelings happens a few times without him even realizing it. Due to the concept of there being no gay people in that universe, he doesn't see what he's doing as flirtatious and sees it as just messing around with his friend while the MC very quickly started believing the ML is gay when he's not. Due to the ML's pirate persona always popping up around the MC and showing his interest in him some officials started putting the MC under protection for safety and surveillance without realizing that they're putting the very pirate they're trying to prevent from approaching inside the same room as him. There's also a scene where the MC's friend group meets some mermaids and the MC tells them the story of the little mermaid but due to him not wanting to see the mermaids cry, he ends up giving it a happy ending. I think that's all I need to say, thanks in advance .
I read the title and one of the first novels that came into my mind was faking straight and then I read your comment and was like it's 100% faking straight.