|Alias||Yuuko Yano (矢野 裕子 Yano Yūko ) (Maiden name)|
|Relatives||Makoto Tamaru (Husband)|
|Hometown||ONLO orphanage, Hokkaido|
|Manga Debut||Line 2; Safe House|
|Anime Debut||Episode 2, Safe House|
Yuuko Tamaru (田丸 裕子 Tamaru Yūko ), née Yano (矢野) is a childhood friend of Yuuki Anzai. She grew up with him in the same ONLO orphanage and used to have a bit of a crush on him. But after graduating from ONLO, she fell in love with and married a human named Makoto Tamaru.
At a young age, Yuuko was placed the ONLO orphanage because of economic crises at home. Although her parents were healthy, they couldn't afford to care for Yuuko and therefore left her at the orphanage. Yuuko became great friends with Yuuki and Tadaya Hiruta and the three would often play together. After she graduated from ONLO, she married Makoto Tamaru and began working part-time as an inspector in the Tsukii Storage.
Yuuko is a petite woman with a slim build noted to be beautiful. She has medium-colored eyes that she wears oval-shaped glasses over, and she has dark circles under her eyes due to being a devil. Her shoulder-length hair is straight and her bangs middle parted; with two strands of hair framing her face.
Like any other devil, Yuuko will transform into a devil at the sight of blood. Her eyes will start to turn red, her irises will turn yellow and veins will appear around her eyes. Her teeth will sharpen into fangs and her nails will turn into claws.
Yuuki has always been a very kind woman, and as a child she was quite meek and shy. She is also quiet and sensitive, and due to her gentleness, she was able to get married despite being a devil. But is stated that, despite her gentle nature, it didn't make her "any less of a devil". She loves her husband dearly, which is why she was very self-conscious about the fact that she was a devil and tried her best not to let him get hurt. She showed great guilt and sadness for hurting her husband.
Yuuko and Makoto had been living together for awhile. But after he accidentally cut his finger one day while cooking, he asked her if she wanted to take a lick. After seeing his blood, Yuuko lost control of herself and accidently drank his blood and stabbed him. After she had come to her senses, she was horrified and fled from her home, but she was later chased down by Division 5 of the Public Safety Department. She was confronted by her childhood friend Yuuki of her actions, to which Yuuko told him about how scared she was that her husband would come to dislike her, but Yuuki scolded her for not explaining the true horrors of being a devil to her husband. Yuuko was later arrested for assault, but her husband forgave Yuuko and showed great concern for her. He promised that he would be more careful in the future.