Anko Koshi

Anko Koshi is the biological younger sister of the story's protagonist, Torako Koshi, and a fellow member of the Shika Club. She harbors an obsessive and deeply distorted attachment toward her sister, treating anyone who attempts to get close to Torako as an outright enemy—earning her the label of an extreme "sister complex" character. Her personality is dark and brooding, marked by severe emotional instability, stalker-like behavior, and a dangerously aggressive disposition.