Jishou Maou to Chuuni Cluster

Kamishiro Kei disappeared for six months as a child and has no recollection of the time. As a high school student, he believes himself to be of the underworld and the rightful heir to the demon lord's throne. His childhood friends, twin sisters Noibara Yuzuki and Akezuki, are accustomed to his unrealistic perception of reality. They often participate in his fantasy, pretending to be his subjects in anticipation of his rule over the underworld.