The Return Of Childhood. (All Might X Reader)

//Kind of a AU, but still not... in this story, One For All give the user immortality. Until, of course, you give it to another.

Toshinori Yagi was once a normal kid who wanted to become a hero, just like everybody else. A kid's dream of becoming something bigger.
Well, that sure is a looooong time ago. Many things have changed. Him, the world, his friends and his... former close friend.
The number one hero haven't seen his childhood friend, (Y/N) (L/N), in over a century. What has she been up to? Why was she avoiding him? Did he do something wrong all those years ago? Something he would like to know, how can he fix it?
A big surprise was waiting not far into the future for All Might. Apparently, a new student is starting in his class...