Shock! The ignorant teenager was used as a stud by some mature sister at the ancestral tomb? The strange disease in his body miraculously disappeared, and he also officially set foot on the path of immortality...

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...