Regular Isekai

Dying wasn't the worst part. The worst part was that someone decided his death was an opportunity.

After clawing his way back from rock bottom — alone, with no magic and no god's help — a young man dies saving a stranger, only to wake up in front of a nervous goddess who insists on giving him a "second chance" he never asked for. When he tries to refuse it, an unfinished system prototype glitches because of him, and he ends up falling into another boy's body: one who did want to die, and who left behind a broken family, a fiancée who no longer exists, and a name that isn't his.

Now he has to survive in a world of magic, fading nobility, and arranged marriages, carrying someone else's grief while chasing the only real lead he has back to his old life: a place called the World Tree. But he soon learns he isn't the only soul dragged into this world — and the other chosen ones, perfectly happy with their new lives of power and harems, aren't going to let him walk away from the lie they've decided to believe.