This shit seems like the plot of Orange and Erased mushed together. Nishimura gets bullied all her life and eventually kills herself, and Takada, who was always in love with her feels a deep sense of regret for not doing anything all this time. But just as he too was going to kill himself, a god takes him back in time and this time he vows to make sure that he does something. So Takada is actually a grown man
. Yes I do read too much manga why do you ask.