Based on Minase Hazuki's C³ (C Cube/Cube x Cursed x Curious) light novel series. The story begins when a high school student named Yachi Haruaki receives a mysterious, super-heavy black cube from his father overseas. That night, Haruaki wakes up to a suspicious noise in the kitchen, and he discovers a fully naked female thief of rice crackers. The girl, Fear, is the first of several surprises that Haruaki receives.