|Height||5'4 (160 cm)|
|Family||Ikuo Takabayashi (Grandson)|
Kensaku Numata (Husband)
|Affiliation||Sakitani Kinenkan Manager|
Keiko appears as an overweight elderly woman with short brown hair that is swept to the left and brown eyes.
She wears a white t-shirt and a yellow apron.
Keiko was introduced as a kind, gentle and warm-hearted grandmother, but she was revealed to be an insane and sociopathic murderer later on.
In the last episode, Tatsuji Chibiki mentioned that she and Kensaku Numata were emotionally depressed about Ikuo Takabayashi's death that this may have lead to Keiko becoming insane in the last two episodes.
Keiko was first seen in Episode 10 when she and Kensaku Numata welcome part of Class 3-3 who came at the Yomiyama Shrine to pray for their safeness, hoping that this action would stop the calamity. The class was accommodated at her restaurant-pension.
In Episode 11, she was revealed to be an insane sociopath. After Yuuya Mochizuki and Naoya Teshigawara found her in a room with a bloody knife, she attempted to kill them. In the process, Yuuya pushed her away from Naoya, causing her to drop her knife and wound the latter's leg. She continues after the two down the hallway. Keiko also killed her husband in a very brutal way and started a fire in the dining room prior to this. After Mochizuki and Naoya escapes from Keiko, he opens an emergency door and Keiko was inside waiting to kill them. The reasons for her insane actions remain a mystery. Though Ikou's death may have affected her greatly to drive her to insanity.
In Episode 12, when Mochizuki and Teshigawara escape by the window, she grabbed Mochizuki's leg. Teshigawara grabbed Mochizuki and pulled both of them out of the window. She grabbed Teshigawara and tried to kill him, but was stopped by Chibiki who proceeded to kill her. Near the end of the episode, Chibiki mentioned that they were Takabayashi's maternal grandparents, and they were emotionally depressed about his death.
- The name Keiko means "top, peak, summit" (峯) (mine) and "child" (子) (ko).
- Her name is translated incorrectly in the anime as "Keiko", due to the enormous number of values of kanji, as in the original novel in Japanese her name "Mineko", in fact, 峯 (mine) means "top/peak" and 子 ("ko") means "child", respectively. Even more confusingly, the official English translation of said novel renders her name as Meiko. No official name has ever actually been given.
- Keiko's surname Numata means "swamp" (沼) (numa) and "field, rice paddy" (田) (ta).
- In the original novel, Keiko killed Manabu Maejima, Izumi Akazawa, Takako Sugiura, Junta Nakao, Shigeki Yonemura and Kensaku Numata with a knife at Sakitani Kinenkan where she then proceeded to commit suicide by biting off her tongue.
- The reason for this wasn't revealed in the original novel and still remains unknown. In the anime, her body count is significantly lower (apparently limited to just her husband), though not for want of trying as she was hunting Yuuya Mochizuki and Naoya Teshigawara from the second half of episode 11 to the first half of Episode 12.
- While everyone else is focused on Izumi and Mei Misaki's confrontation at dinner, there are two scenes showing Keiko preparing to murder her husband and burn the inn to the ground.
- Main article: Keiko Numata/Image Gallery