The incomparably beautiful girl, “Mamori Honjo”, continued to be seen through lustful eyes by boys due to her beauty, and through jealous eyes by girls. Boys turned into stalkers one after another, and she faced extreme bullying from girls. As a result, Mamori developed a fear of humans and began to tread the path of a hikikomori. One day, while she continued her hikikomori lifestyle, a crazy stalker entered her home, which was her sanctuary, gripping a knife. The stalker murdered her parents, and Mamori herself was on the verge of losing her chastity. In desperate resistance, she ended up killing the stalker. After such a horrific experience, Mamori lost consciousness and before she knew it, she was summoned to a different world. When she woke up, there was a small cave and a glowing blue crystal called a “Dungeon Core” in front of her. Upon touching the Dungeon Core, Mamori inadvertently became a being called a “Dungeon Master” who was responsible for growing the dungeon. She made a resolve. She would create an impregnable labyrinth where no one could trample on her anymore, and perfect her reclusive lifestyle there! And so, Mamori mercilessly slaughters any intruders who set foot into her dungeon, transforming into the strongest hikikomori. . . or rather, the strongest Dungeon Master.