This is a Blue Exorcist fanfiction with Rin X OC. OC is a Nephilim, or the offspring of a demon and a human. Her name is Rio Adachi, and she is like a neko, looking like a human but with cat ears and a tail. Her role in the story is that she was a familiar to Shiro Fujimoto, at least, publicly. In real life, Shiro taught Rio how to fight and protect herself and was like a father figure to her. When Shiro died, Rio was passed down to Rin. Now Rio is his familiar. Rin didn't know about Rio because Shiro had her hide herself from him, but he ordered her to protect him, so that Rio had to follow Rin to make sure he was safe. Rio can transform into a cat like Mephisto, so Rin keeps her in his backpack during day school. During the Cram School, she turns back into her original form. This results in multiple students having a grudge against her for being a Nephilim, and not trusting her. Her weapon is a a spear that that can move around in the air because of some fingerless tech gloves she wears. The gloves allow her to control the spear. Rio wears an white, ed, collared shirt and a leather jacket. The shirt is ed to her s, so that some but not too much cleavage is shown. Rio wears some baggy white pants and some black flats. She also wears a silver necklace with a ring on it. The ring has a pair of silver wings and a diamond in between them. The ring is the last thing she has from her dead human mother. Rio's hair is silver and her eyes are a crystal blue.