I think it's important to realize that MC doesn't want to do anything in Taekin's body without permission. His reasoning is solid... he would obviously try to help if Taekin was back in his own body and Heechan also keeping his body, but that's not what's happening. In fact, Heechan doesn't think he jumped in front of the car because of the bullying, that there must be something more to the story. If Heechan thought it was simple enough to take care of bullied to get his body back, he would've done it. But he also cares about Taekin and Taekin's mother, and I personally think that's really sweet of him. He also values Taekin's agency and doesn't want to permanently mess up his life. It makes sense, doesn't it?
Lol there was some people in the webnovel comments that really wanted mc to get with Mujin to the point of giving a bad review bc their endgame ship wasnt canon. I think they're both meant to be leads you can root for, it's just that one side lost. But just wanted to give an idea that some people might be disappointed /shock
The story is a little intriguing ngl. Red flags aside, hearing the MC talk about his backstory even briefly made me feel bad for him. I know he's mentally unwell but I feel like from subtext it's basically implied that he doesn't try to escape because he doesn't know how good he could have it, having been born in such a miserable place. His obsession is all he can use to ignore how horrible his life is, and despite all that, he still cares for his useless parents... anyway I'm curious to see how his character could possibly develop. It FEELS like you can only go up from there, but it's not like what the ML is offering him could be remotely interpreted as salvation... So what, then?