Momo Souma

Momo is curious, gentle and more observant than the adults around her realize. Although she has not been given a full explanation of Momiji's place in the family, she notices him and becomes increasingly interested in why he seems familiar.

She is also willing to act on that curiosity. Momo secretly follows Momiji and approaches Tooru when she realizes that Tooru knows him, eventually trusting her with a deeply personal request.

Her interest in violin is tied to the same longing for connection. Rather than being only a hobby, learning the instrument gives Momo a possible point of contact with the older boy she wants to understand.

Momo has no supernatural abilities and does not carry one of the Zodiac spirits.

She studies violin after becoming interested in Momiji's playing. Her musical training creates another parallel between the siblings despite the efforts made to keep their lives separate.

Momo is also adept enough at navigating the Souma estate to show Tooru a concealed route inside when they meet.

Momo's appearances reveal the long-term consequences of the decisions surrounding Momiji's childhood. She grows up within his biological family while being prevented from understanding why an older boy so similar to her remains at a distance.

Her curiosity eventually becomes explicit when she encounters Tooru. Momo asks Tooru to find out whether Momiji would be willing to become her older brother, unaware that this is already their biological relationship. She also reveals that she took up violin partly because she hoped they might someday play together.

When Tooru carries Momo's words back to Momiji, the request gives him confirmation that his sister has independently reached toward him despite their father's efforts to keep them apart.

Momiji Souma is Momo's older biological brother. Momo does not initially know the truth of their relationship, but she feels drawn to him and asks whether he would be willing to become her brother.

Tooru Honda becomes Momo's intermediary because Momo recognizes that she knows Momiji and trusts her to deliver her request.

Momiji and Momo's father deliberately keeps the siblings separated in order to preserve the family arrangement created after Momiji's mother's memories were altered.

Momiji and Momo's mother raises Momo without acknowledging Momiji as her son, leaving Momo to notice the resemblance between them without understanding its cause.