A CCCat who was found by a mysterious winged man claiming to be some kind of angel named Rin. He mentioned a name once, "Yuu," and the CCCat liked the name enough to begin calling himself that, despite Rin's dislike of the notion. With no actual protest to the name choice, Rin slowly began to tell Yuu about the man he was now named after. He learned many things, and found himself wanting to meet this man, which he hoped would happen soon. Rin was searching for this man, in fact. 

Yuu learned that the man he named himself after was called Mizushima Kazuki (he would never understand why some humans said their last names first), and that "Yuu" was an affectionate nickname given to him by another human, Rei. 

Yuu learned that Kazuki was presumed dead, with only whispers among other supernatural entities that Kazuki had become a demon.

So now he searches with Rin for Kazuki, eager to meet this man he has only heard stories of. Despite Kazuki being just a person from stories he was told, Yuu could not help but to hold this man, demon or not, in high regard with how Rin spoke highly of him.