There are darknesses in life and there are lights, and where there is light there is always a shadow that comes with.
He was once one of the lights, the light of all lights that had matched others' candles to save them from their darkness, made others smile, have and gain hope, forget their troubles.
He was a hero who was burdened with far too much and leaned on others far too little, but the brighter the light, the deeper the shadow.
Determined to save the world, the survivors plotted and made a seal, and put it on him as he was their hope, the child of prophecy, the hero, their salvation.
It was a seal created to send him back in time and when that time had come he was the last to have lived and the first to see the world disappear with Kaguya ruling, the black zetsu her servant, and the white zetsu's as her subjects, and the Juubi her pet.
There was no one left as they had protected him to give him this chance and the time that was needed for the seal to activate.
It had been barely enough.
A broken hero tasked with even more burdens to carry but this time he will keep his promise to save the world and stop the cycle of hatred.