Forty years have passed since dungeons from different dimensions appeared on earth. By now, most energy resources are coming from the dungeon, its’ existence had already been integrated to everyday life. Our protagonist, Toudou Tsukihiko was the man who dreamed of becoming one of the seekers who venture into those dungeons. Unfortunately, he lacked the qualification to enter the said dungeon, namely the existence of 『Slot』, and thus had no choice but to spend his life in boredom. Until someday, a certain event became the turning point of his life…