The manga based off the best-selling The Decagon House Murders novel by Yukito Ayatsuji! The members of a particular university's Mystery Club travel to a ten-sided house on a remote island...which just happens to have been the scene of a gristly, and unsolved, mass murder. Armed with details of the murder and keys to the property, they set out to dig deeper...but can they trust the facts" of the case? And moreover...can they trust each other?"
The seven members of a college mystery club head to Tsunojima Island, the site of a mysterious murder-homicide and ten-sided house built by the murdered architect Seiji Nakamura. Before long, the students start dying strange deaths, and the survivors find themselves locked in a battle of wits with the murderer... Meanwhile, back on the mainland, former club member Minamikawa visits the grave of Chiori Nakamura, another former club member who died in a boating accident. While there, she finds something that turns the case on its head...