I'm currently reading a story on here called Half of Me that plays with the body swap element, only the younger boy's body refuses to wake. Despite not caring at first, the MC is actually trying his best now to 'save' the younger boy, not simply to get back to his own body but because the boy deserves to have someone help. It's a good read so far, I recommend! It's what led me here but looks like this story is really dismissive towards the suffering boy so I don't think I'll be reading it XD Besides, from the comments it looks like the MC never gets to return to his OG body so this imposter body-snatcher vibe feels uncomfortable!
Hate this kind of trope where the OG char just died miserably and then another person takes over their body and has a happy ending. Doesn't the person who suffered through all of that deserve to have their happy ending too?