C³, also known as C Cube (シーキューブ) or Cube×Cursed×Curious, is a Japanese light novel series written by Hazuki Minase, and illustrated by Sasorigatame. C³ is about a high school student named Haruaki Yachi, who receives a mysterious black cube from his father who is overseas. That night, Haruaki is woken by a noise and is surprised to find a girl named Fear Kubrick in his kitchen eating rice crackers. Haruaki confirms that she is the cube, but knows nothing about her past other than that she has a curse on her which she wants broken. Breaking the curse though proves hard as there are organizations that seek to capture or destroy Fear, along with her dark past as a "Cursed Tool" which comes to light. Haruaki vows to protect her though, and is joined along by other allies/friends as the series progresses.
The series was later adapted into a manga, and appeared as a serial in the manga magazine Dengeki Daioh from February 26, 2011, to January 26, 2013. ASCII Media Works then published the chapters in three bound volumes. An anime adaptation came next, which aired on various networks from October 1, 2011, to December 17, 2011. Twelve episodes aired in all, excluding an OVA to the series which was later released on April 25, 2012. Funimation acquired the license to the anime for a North American release late in 2015, and the complete series along with the OVA was released in march of the following year.
Plot
The story begins with high-school student Yachi Haruaki receiving a mysterious super-heavy black cube from his overseas archaeologist father.