|Hometown||Meguro Ward, Tokyo|
|Manga Debut||Line 45; Corvus Corax|
Saki Sumimori, at one point in her life, married Katsuki Sumimori. Some time into their marriage, Katsuki spoke out about his desire to have plastic surgery. However, Saki was against it since it would simply be too sad.
A year later, Katsuki disappeared and came back after a while; 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. When Mayu got her job at the CCC, Katsuki, Saki, and Mara were told that Mayu would only do clerical work at a trading company when in reality, she was working for an organization aiming to exterminate devils from the world. Saki also got sick and currently, Saki lives with her family in Tokyo.
Saki is a beautiful middle-aged woman with a very youthful appearance. She has straight black hair which she wears in a low bun with bangs covering her forehead and two locks of hair framing her face. At times, she lets her hair down in which it is seen being slightly below shoulder-length. She has light-colored eyes and long eyelashes. Her youngest daughter, Mio, is very similar to her. Due to her illness, she is seen having tubes in her nose and sitting in her wheelchair.
Saki is a genuinely kind-hearted and soft-spoken person who is considerate of everyone around her and always appears calm and friendly, never being provoked by anything. Even in violent situations, she will try to be calm and solve problems with no violence. She cares for her family and is protective of and loves her husband and daughters deeply. Unlike her husband, Saki sympathizes with Mayu the most and is very understanding of her and the way she is. According to Mayu, Saki holds on to every little thing.
Katsuki is Saki's husband where they fell in love with each other and eventually got married with four daughters. In the past when Katsuki got plastic surgery, Saki was devastated that she couldn't be there for him during a tough period in his life, and that they couldn't be two people joined in one marriage. At the same time, she was more than happy that he came back to her. Currently, Saki has mixed feelings towards her husband. While he is dear to her and she loves him, Saki feels like he is hopeless since he is very rude towards Mayu. He told her to get out of the house if she shielded Mayu. She also describes him as arrogant, pretentious, cowardly etc, which is what she claims is traits Katsuki shares with Mayu. Despite that, Saki really understands Katsuki like no one else.
Mayu is one of Saki's daughters. When Katsuki would adore all their daughters except Mayu, Saki being her mother, sympathized with her and adored her as well. Saki genuinely loves Mayu and is very protective of her, as when the first time she saw Mayu after the CCC raid, she was seen crying uncontrollably, tried to jump off her wheelchair to embrace her, and held her hand during the entire time they were going back home. Saki only wants the best for her and while Saki apologizes for fussing over her so much, she says that as long as Mayu is healthy and safe, she is content and happy. She ensures Mayu that she is strong and will be able to overcome her trials. Unlike the rest of the family, Saki truly understands and trusts Mayu, as Mayu is the only one who has ever received Saki's old notebook to read, containing the story of her Katsuki got plastic surgery and their story together. In it, she also expresses that Mayu and her "boyfriend" Takeshi Makimura will able to take a different path than she and Katsuki did. She hopes that Makimura can always be by her side, and Mayu always at his.
- The name Saki means "sand" (沙) (sa) and "chronicle" (紀) (ki).
- Saki's surname Sumimori means "housing, live/living, dwell/dwelling, reside, inhabit" (住) (sumi) and "forest" (森) (mori).
- Saki is presumed to have COPD.