|Former Affiliation||East Bay University|
|Manga Debut||Line 28; Support Tech Gardens|
|Anime Debut||Episode 9; Command|
Kousuke Chizu (千頭 康介 Chizu Kōsuke ) is the adoptive father of Nanako Tenjo, who took her in after the death of her parents.
Kousuke Chizu was originally a professor who used to teach at a university called East Bay University. Kirio Kikuhara also attended this university. At some point, he adopted Nanako and two other children, but he never saw Nanako playing with them, as she had closed off her heart following a traumatizing incident. When he retired, he started, for a few years, to hold study groups at his house. It was just a hobby, but all kinds of people, like researchers, politicians, and students would come. It is due to these study groups that Nanako got to meet Kikuhara, and because of his influence, Nanako got over her trauma and directed all her hatred towards devils.
In 2007, Nanako "moved out" to attend college (in reality, she joined the CCC), to which Kousuke said that he would miss her. He also told her that he would send her allowance so she could live by herself, but Nanako insisted that she would be fine.
Kousuke is a short, elderly man with wrinkles on his face. He has grey short spiked hair and a straight hairline. He has visible jawbones and small, light-brown eyes.
Kousuke is a sociable man, as his idea to start a study group united a lot of people and himself with other people with the same interest. He is also kind-hearted and considerate as he deeply cares about his children and their well-being. He regrets not saying much when Nanako sounded prejudiced while talking about devils, since he claimed he couldn't say much considering her circumstances. However, despite Nanako's personality traits and actions, Kousuke is confident that Nanako is a very kind-hearted and considerate, but blunt and awkward girl.
To find out more about Nanako, her motives for killing devils, and how she met and developed a relationship with Kikuhara, Takashi Sawazaki discussed these matters with Kousuke, her adoptive father. Kousuke speaks out about Nanako's attitude after the death of her mother and Morisawa, and how she came over her trauma when she met a certain someone; Kikuhara.