|Hometown||Meguro Ward, Tokyo|
|Manga Debut||Line 33; Children (Mentioned)|
Katsuki Sumimori, at one point in his life, married Saki Sumimori. Some time into their marriage, Katsuki spoke out about his desire to have plastic surgery. Saki was against it since it would simply be too sad. A year later, Katsuki disappeared and came back after a while. When he did, he had already gotten plastic surgery. Although Saki was sad that she couldn't be there for him during that tough period, she was happy that he came back to her. Soon after, they settled down and formed a family, having four daughters; Mana, Kaori, Mayu, and Mio. Katsuki also continued to work at his unknown workplace. However, it is known that he has a lot of connections, as a friend of Katsuki's were friend with Kirio Kikuhara. This is where Mayu got her job at the CCC. Although the CCC was actually an organization aiming to exterminate devils from the world, Katsuki, Saki, and Mara were told that Mayu would only do clerical work at a trading company. Currently, Katsuki lives with his family in Tokyo.
Katsuki is a tall, middle-aged man with some age-marks who is seen dressing very professionally. He has short, straight, medium-colored slicked back hair, and sharp, light-colored eyes. He also has a defined facial structure. Katsuki had plastic surgery before the births of his daughters. One of his daughters, Mayu, looks exactly like him before he got plastic surgery.
Words that can describe Katsuki are arrogant, pretentious, cowardly and fragile. In that sense, Mayu takes after her father. Katsuki prefers to deal with tough decision alone, as he did not discuss the matter with plastic surgery with his wife as much as he was supposed to, and he decided to be alone. As Mayu claims, Katsuki favors his others daughters over Mayu and fawns over them. He likes Mayu the least and does not fawn over her one bit like he does on his other daughters. Mayu has claimed that when Katsuki is drunk, he has said that Mayu takes after her late grandmother, that she is ugly and hard on the eyes. His words would result in her daughter taking the same path as him, as she would start to feel ugly and eventually planning to get plastic surgery.