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
I FUCKING LOST IT WHEN THE DOG IS ALSO NAMED KHAN WHY YOU GOTTA DO MC LIKE THAT BRO
FOR REAL, THE DOGGGG THAG DOGGGGGGGGGG CRYING MY BALLS OUT