Sayu is a young girl with soft, wavy light-brown hair and gentle hazel-brown eyes. In her earlier years, she styles her hair in twin pigtails, her right side tied with a red ribbon and the left with a plain red hair tie, giving her a playful and youthful charm.

Following the time skip, Sayu’s hair has grown longer. She continues to wear small pigtails tied with red ribbons, while the rest of her hair is left down, reflecting her efforts to appear more mature while still retaining a part of her childhood innocence.

Sayu is a devoted and caring friend, especially toward Miuna Shiodome, often going out of her way to protect her and bring her happiness. Despite her young age, she has a strong will and strives to be seen as mature particularly in the eyes of Kaname Isaki, whom she wants to view her as more than just a child. After the timeskip, Sayu develops into a more self-assured and independent young girl. However, her confidence occasionally falters when faced with matters of love, especially after Kaname’s return from hibernation, showing a more vulnerable side to her otherwise determined personality.

Sayu Hisanuma was a third-grade elementary school student at the beginning of the story and was often seen alongside her best friend, Miuna Shiodome. The two shared a close bond, particularly during the time Miuna was struggling with her emotions after the loss of her mother and the arrival of Akari Sakishima in their lives. Sayu stood by Miuna, helping her cope and offering her support through those emotional transitions.

After the timeskip, Sayu enters middle school with Miuna. During this period, she matures significantly, both in appearance and attitude. She begins to study more seriously, aspiring to become independent. Despite her efforts to move on, her feelings for Kaname Isaki who had gone into hibernation remain strong. When Kaname finally awakens, Sayu’s lingering feelings and emotional growth come to the surface, leading her to confess to him and marking a turning point in her personal development and their relationship.

Kaname Isaki
Sayu begins to develop feelings for Kaname after he encourages her to open up and helps her become friends with Hikari Sakishima. These feelings remain steady and even deepen after the timeskip, as Sayu enters middle school and matures emotionally. Though she tries to focus on her own growth and independence, her affection for Kaname only grows stronger.

Despite Kaname initially retaining lingering feelings for Chisaki Hiradaira, a quiet bond forms between him and Sayu. When Kaname makes a remark suggesting it’s better for Manaka not to experience love, Sayu challenges his perspective, calling it selfish and expressing how important her own feelings are. She later tells Miuna that her feelings for Kaname were the reason she was able to move forward in life, and resolves to confess her love to him, regardless of the outcome.

She eventually sees Kaname overhearing a private conversation between Tsumugu and Chisaki about their mutual feelings, prompting a critical emotional turning point. Sayu confronts Kaname afterward, bravely expressing her emotions. Her heartfelt confession surprises him, especially because he believed no one had been waiting for him after the Ofunehiki. Sayu’s sincerity moves Kaname, leading him to begin seeing her in a new light not as the child he once knew, but as someone his age and emotional equal.

Miuna Shiodome
Miuna has been Sayu’s closest friend since second grade. Sayu deeply values their bond and is fiercely protective of her. When Miuna’s father, Itaru, and Hikari’s sister, Akari, begin a relationship, Sayu initially tries to sabotage it out of loyalty to Miuna, believing it would protect her from emotional pain. However, this backfires and upsets Miuna, who respects Hikari’s ideals. Realizing she hurt her best friend, Sayu becomes remorseful.

Later, Sayu reveals to Kaname that she never wanted to be one of the girls who ignored Miuna she wanted to be someone special to her. Miuna overhears this heartfelt admission but chooses to remain silent, a moment that reinforces the strength and unspoken understanding in their friendship.