南崎 伊鈴々

The protagonist's stepsister. After her mother remarried a month ago, she lives alone with the protagonist in the house while their parents are away.

She attends an all-girls school and handles all household chores by herself at home. Despite appearances, she's actually a dependable person who takes good care of others.

Her personality is bright and innocent. She loves cleanliness, especially baths. Since she'd wanted an older brother since she was little, she's become very attached to the protagonist, even though it hasn't been that long.