Kiryuu Shizue

The sister of the protagonist's father, she is a single but motherly woman. She always has a somewhat fragile smile on her face.

She is more like a mother to the protagonist than his mother, having cared for him since he was a child. For some reason, she tries to keep her distance from the protagonist, who has returned home.

She feels estranged from her family's fate and hopes that the protagonist will be able to break through it.

Spoiler

She is actually Hayato, Yuzuha, and Hinaki's mother. She married her own father and had children with him. She doesn't like what her mother Reika is planning, to have Hayato take the place of his father and make more inbred children for Reika to survive on but there isn't much she can do against her.