The manga centers on middle school teacher Umi Yamauchi, who one day sees a news report of the murder of Yūki Suzuki, his friend from his own middle school years. A few days later, Umi's girlfriend Tamao...

Masuda Keima, a lazy high-school boy who prefers to laze around and avoid working, gets summoned as a dungeon monster by a girl avatar named "Dungeon Core No. 695" who is the dungeon core of the mighty one-room...