She is mean rude and sharp tounged, she cares alot about yuki and will defend him no matter what situation he is in. She is also very sarcastic and witty
(Copy and pasted sorta from the danganronpa wiki since she is basically a genderbend)
In Yasu's childhood, her mother was diagnosed with an unnamed disease that appeared to have symptoms similar to Alzheimer's disease— causing her to forget who her own daughter was. Her mother's doctors also forbade Yasu from addressing her as 'mom', or 'mother'.
Her condition eventually led to her unfortunate death, and possibly, Yasuke's rather ambivalent and aloof personality.
Although she claimed that her death made her feel “free”, it is heavily implied that she still harbors a large amount of guilt and grief over her demise, despite it being so long ago. This is shown through her lonely, and sour personality. Her death may also be responsible for her current profession in the field of neurology, due to the bitterness felt on her behalf towards her doctors, who could have done 'better' in her eyes.
Yuki and Yasu have been friends since her childhood. During the time when both of them were in elementary school, Yuki began working on a sand sculpture based on the Sagrada Familia church. However, a month later, it was destroyed by an unknown culprit. After seeing him break down in tears and weep for almost a whole day, Yasu decided to go and search for the perpetrator.
Yasu's investigation eventually wound up to a dead-end, as she had never found any witnesses. Not being able to find out anything useful discouraged her. While she was sitting on a bench in front of the remains of the sand sculpture, Yuki ran up to her with a large smile and whispered in her ear that he was the culprit who destroyed the sculpture all along, asking her to keep it a secret. When asked for a reason, he replied that he did so by accident. Truthfully, he had done this to get Yasu out of her house, upset that her mother's condition had led him to become more withdrawn than usual.
In the years following the death of Yasu's mother, Yuki became the person that Yasu felt she could always lean on. he promised to always be there for her, which helped develop his stronger feelings towards her.