Naruto, The Mercenary of Fate.

After The Nine Tailed Fox invades Konoha The fourth Hokage seals the Nine tail Into one of his twin children, Naruko, the Shinigami does not take Minato and Kushina's soul as payment, having claimed that the debt will be payed for in the future. Years later we follow the story of a young child named  Naruto. Having been Neglected by his parents his whole life in order to train his twin sister as the child of Prophecy, he becomes distanced greatly from them, and losing his standing as heir to the Namikaze clan was the last straw, so he runs away from home and stumbles upon a cave, the inside made of glass and he finds a contract, one that makes him a mercenary, to fate.  Now Naruto finds himself completing quests in order to obtain great power, many of the quests themselves however...are literally out of this world. Watch as Naruto changes not only his world but many more.