The September issue of publisher Kodansha Afternoon revealed that the adaptation of the manga The Decagon House Murders will therefore enter the “final arc of the 'island' tragedy” in the next issue of the magazine.
Synopsis
Students from a university mystery club decide to visit an island that was the scene of a horrific multiple murder the previous year. Predictably, they are then picked off one by one by an unseen killer. So is there a madman on the loose? What connection is there to the previous murders? The answer is a bombshell revelation that few readers will see coming.
The manga was released in August 2019. The third volume of the manga was then released in Japan on March 23.
Source: ANN