She have gray hair for anime.
She is depicted as a quiet, nearly emotionless young woman with occasional destructive behavior, such as wrecking the student council room. She is afraid of perfection due to when she was competing for role as heir and was forced to act perfect. She has difficulty expressing herself, which sometimes results in Manabe making decisions for her.
Unlike most girls at school, she does not see Yuki as a prince, but as just another boy, even seeing him as being lonely.
During their childhoods, their mothers competed to have their own child named heir, a struggle that ended when first Manabe withdrew himself from the running, then Machi's mother bore a son. Machi lives apart from her family because her mother believes she resents, and is a danger to, her younger brother for supplanting her, an accusation she did not contest even though it is false.
Her different attitude and troubled behavior catches Yuki's eye, and he makes multiple attempts at befriending her. When Yuki and Manabe visit Machi's apartment, Yuki learns that because of the pressure to be perfect when her mother was competing with Manabe's, Machi finds perfection so disturbing she has a compulsion to mar anything too orderly, such as trashing neat rooms, walking through newly-fallen snow, and breaking pieces of a new box of chalk. Machi develops feelings for Yuki, and when Tohru Honda is in the hospital and he needs to reach out to someone, Machi is able to confess to Yuki.
- Like the youngest Somas, Machi likes the fictional anime Mogeta, and treasures two character figurines that Yuki gives her.