Bleach

I will give some information from Bleach That one of popular anime, I don't want to give spoilers so it was so short :)

Ichigo Kurosaki (Orange hair Cool Guy) is a teenager who has always been able to see spirits. The story begins with the sudden appearance of an oddly-dressed stranger in Ichigo's bedroom. This stranger is the shinigami Rukia Kuchiki, who is surprised that he can see her. While they are talking a Hollow comes. After Rukia is badly wounded while fighting to protect Ichigo, she decides to transfer half of her powers to Ichigo, hoping to give him a chance to fight the hollow. By accident Ichigo absorbs all of Rukia's powers instead, and he defeats the Hollow easily.