Hakuya Mitsumine (三峰 白夜 Mitsumine Hakuya?) is Kobeni Yonomori's fiance who suddenly appears on her 16th birthday with his little sister Mashiro Mitsumine. He and his sister start living in the same house as Kobeni and her own sister, Benio Yonomori.
Hakuya is a tall man with spiky black hair. His bangs cover his right eye, because of the scar he and Kobeni got as kids. He can make out light but he is used to it. He is a taciturn and mellow character, a bit oblivious to the world and slow to catch up on things.
Later, Hakuya is revealed to be an Inugami and possesses some rather unusual abilities such as an inhuman speed and endurance, allowing him to jump long distances. He also states that he can shapeshift into a black dog but refuses to do so.
Hakuya appears to be shy, serious, and quiet so his personality remains on a small known intelligence. It is mentioned by Mashiro that he usually does not like sweets, but still ate it because Kobeni made it. Although he doesn't show his emotions through expressions, Kobeni can usually tell what he is feeling.
He is shown to have patience and control over himself most of the time, rarely showing any kind of reaction or emotions to his surroundings.
Kobeni is Hakuya's fiancée and childhood friend. They used to play together as children when Kobeni visited his homeland in the mountains, though Kobeni did not initially realize it was him since he was still in his Youma form. During that time, Hakuya lost sight of Kobeni for a brief moment before she fell off a cliff, almost losing her life. Regardless of having his right eye scarred from falling off the cliff with her, Hakuya passed on half of his inhuman power to her in order to save her life. As a result of passing on half of his powers Kobeni was left with a weak constitution because his powers were not completely compatible with her body. Nonetheless Kobeni lived through the experience.
It is stated by Mashiro many times that Hakuya was raised to become Kobeni's future husband and has no objections against the idea. Because of his dog-like nature, Hakuya is protective of her and follows her around, always keeping an eye on her and helping her whenever he can. He had also flat out said that he liked Kobeni when her friend, Mayura, asked him what he liked in attempt to help Kobeni figure out what to give him as a Valentine day present during episode 4. Also, though his outward appearance does not show it, he actually gets extremely happy whenever she reciprocates his feelings through her little comments and actions.
Mashiro is Hakuya's little sister. Because of his blunt personality, Mashiro is very vigilant towards him and explains many things that Hakuya can't understand. This causes Mashiro to move in to the Yonomori's household alongside him. Mashiro has shown to care for her brother and often seeks him out for protection from Benio.
Mashiro is also Hakuya's love adviser and helps him to understand many facts about Kobeni that Hakuya himself can't understand such as finding a present for her.
Benio is Hakuya's future sister-in-law. Benio has shown to be jealous of Hakuya and can't get along with him because of the idea of him taking her little sister away from her and her own siscon personality. Despite her aggressive nature towards Hakuya, he doesn't seem to care and ignores her.
Shirayuki is Hakuya's mother.