Having lost their parents in a fire when they were young, Haru and Yuu, an older sister and younger brother, have been living alone together away from any of their relatives.
Haru, the older sister, is bewildered by her younger brother's romantic feelings and unusual obsession with her, but ends up nonetheless in an intimate physical relationship with him.
The younger brother's obsession with his older sister is related to a memory from his past.

Official Translations:
English, Korean