After his mother's death, Kuro Takagi transfers to Yotsuji Private High School where his father is the proprietor. But Yotsuji is no ordinary school. It holds a strange rule of “No students on campus after...

Caught with a severe fever, Tobio Ikuse, a second-year high school student, was forced to miss his school trip on a luxury liner with his schoolmates. Four days later, Tobio hears the news about the disappea...