Working as a private tutor for her younger brother, the sister has always helped him study due to his poor academic performance. Over time, his dependence on her gradually transforms into romantic feelings. The brother becomes increasingly drawn to his sister's body, and they make a pact: in exchange for better test scores, she will allow him to have sex with her. One day, the sister arrives at his home in a nurse's uniform, worried about his health after hearing that her now-adult brother has fallen ill. As a caring nurse and devoted sister, she struggles with her growing desire to touch his body, torn between genuine concern and uncontrollable lust.