Shingo’s little sister, who until recently was the only girl Shingo didn’t fear, mainly because she dressed like a boy. However, one day she started dressing like a girl and recently has gone through a big growth spurt, which makes her look much more ‘mature’ to the point she is constantly mistaken for a teenager (while she is in sixth grade). Subaru has a brother complex and is determined to be the only woman in Shingo’s life (even wishing to have her brother’s child and training to become her brother’s woman, believing under a misunderstanding that means going through bondage training), where because of this, she usually treats Shingo’s friends poorly, tricking them to do chores around the house when they come over. Becomes extremely possessive and jealous when other girls hang around her brother. Their mother doesn’t seem all too motivated to disapprove of Subaru’s feelings towards her brother, and is even shown enjoying movies with incest, even stating that the best woman for him would be his sister.