Yorusuke

The tosa-inu inugami older brother of Kuro. While not related by blood they have spent nearly all of their lives together. While initially Kuro was marginally stronger than Yoru, he has grown far stronger than her (and potentially even the  near untouchable gods like Tsukuyomi and Amaterasu). While originally being weaker than Kuro he made it a point to become stronger than her in the interest of protecting her, which became more necessary as they got older and it became more obvious how oblivious she was of the world. He is extremely protective of his little sister and will quickly resort of violence to protect her, but generally ignores anything else while watching over her since very few things can do any real damage to him. Both kuro and himself were born as yokai and were not transformed post-mortem.