Share your best ideas for an manga/anime

Mine is: What if a person with depression, anxiety and a whole lot of trauma and shit has the chance to go back in time and change his/her past.(the person who gave him/her that opportunity used uhh, let say Tec cuz I don't wanna say God, too many shit turn out like that, and the entire plot goes around that one mysterious entity). Obviously, he/her accepts and then only change all the really bad stuff because limited time. Um 6 years to change it. but it after he/she changed it, the world went for the worse. Basically he/she has to deicide whether sacrificing themselves is good to save the majority or if everyone has to fight for them selves. Cuz the world has been shit to him/her they chose the second option. then slowly people start to realize that they are in this situation because of that guy. Some people don't blame him/her and others do, did he make the right decision or not? he/her meets ppl along the way but there all just trying to use him/her and the little few that don't die.

LMFAO came up with this on the spot cuz i couldn't remember the others