Raised in an institution, nurse Koko is repeatedly taken by her stepfather, the hospital director, and her stepbrother, a surgeon, in examination and operating rooms night after night. The family who took her in during childhood continues to dominate her body. One day, an amnesiac patient arrives at the hospital, and she realizes he is the same boy she once called "big brother" at the facility. In that moment, long-buried secrets come to light, forcing Koko to make a new choice.