Bleach: Ichigo Kurosaki

A foreign soul invades into Ichigo Kurosaki's soul, but rather than it taking over, their souls assimilated into one, giving Ichigo future information and awakening his Soul Reaper powers at the ripe age of 9...

But not even a few seconds later, him and his mom were attacked by a stray hollow.

Realizing that his mom had just lost her powers, he defended her with his life, promptly causing his death and sending him to the Soul Society, where he would later be deemed the Greatest Shinigami in History!

Watch as Ichigo Kurosaki paves the way for a better Soul Society and becomes a legendary figure in the Gotei 13!
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Just writing this for fun!