Naruto: The Master of Shadows.

Dave doesn't remember how he died and very little of how he lived, he was a young league of legends player who left the game because he was bullied for his shyness and excessive fatness and in the end he isolated himself from everything and dedicated himself to the game but apparently this led to his death.
However he was given a second life in the Naruto universe with the skills and a share of the memories of his favorite champion, Zed!