Not your average isekai. Trust me

Kai is a miserable person, his life is so shit that he’s about to end it right now. However a girl comes and saves his life and later on he returns the favour by saving hers but at the cost of his. He is sent to heaven and told by god he wasn’t supposed to die because he had planned for him to jump off the cliff that girl just saved him from?!
Now he is told that he will be reincarnated in another world but because he made a mistake and killed him in the wrong time as a way of saying sorry he gets to keep all his memories. “Now what…..? Im not ready to start another life i just died for god’s sake”