Ryoba Aishi

'''The mother of Yandere-chan and the current wife of the father. '''

It is speculated that she is the same girl featured in the mysterious tapes whom the Journalist confronted. She is out of town for 10 weeks for Story Mode because of an unknown reason.

Background
When Yandere-chan's parents were in Akademi High in the 1980's, Yandere-chan's father was the mother's senpai. The mother killed the Phantom Girl with a knife  in the third floor girls' bathroom, but it's not outright stated (although heavily implied) that she did it for him.

The mother has no other children other than Yandere-chan.

The Mother has a job related to the game's lore. YandereDev has planned to drop hints about what the job is soon.

Appearance
The mother has a very gentle face. She is identical to Yandere-chan, but older. She has the same hair color and hair style as her daughter.

Personality
It is very likely that she is a murderer. In the original intro, Info-chan gives a hint about it when saying "So, history is repeating itself?" and "It is in your blood, after all" to Yandere-chan, although this intro is now outdated.

The mother seems to be willing to take serious action to get jobs done, as seen by how she dealt with the Phantom Girl. It's not exactly known what made the mother go that far.

She also seems at least somewhat intelligent if she was able to murder a girl and get away with her crimes. The way she took down a girl with only a knife probably means that she's tough enough to take another student down both mentally and physically.

She has a loving relationship with her daughter, who she adores.

Yandere-chan
The mother might've passed down her murderous traits to her daughter. In the second intro Yandere-chan expresses feelings about wanting to kill Osana Najimi just so that she can have her Senpai, presumably like how the mother killed a girl for unknown reasons. Yandere-chan doesn't have a negative relationship with her parents. The dev states that she's just indifferent to them. Yandere-chan believes her mother to be a lovely human being, though she may not know what her mother did in the past. Yandere-chan's mother loves and adores her daughter very dearly. The mother knows about Yandere-chan's lack of emotion.

Yandere-chan's Father
She married him and had one daughter, Yandere-chan. While they were in high school Yandere-chan's father was Yandere-chan's mother's senpai. The father doesn't seem to know about the mother did, though only time will tell.

Phantom Girl
Yandere-chan's mother killed the Phantom Girl with a knife in the third floor girls' bathroom. The reason for the homicide is unknown, or how dangerous the Phantom Girl was.

Trivia

 * Her name came from Basement Tape One.