Twenty-six-year-old Heita Tsukigami falls asleep from exhaustion while riding the train home, only to awaken in a bizarre world unlike anything he's ever seen. His first destination isn't a magnificent fantasy kingdom, but a gigantic junkyard filled with strange gadgets where he's nearly crushed along with the garbage. After being rescued through an encounter with a mysterious girl named Emma, Heita learns that he's been transported to the Kingdom of Montgomery, better known as “Monty Paradise,” a strange realm ruled by the spiteful King Piritos.

Even more troubling, portions of Heita's memories have been taken from him, marking him as one of the people known as the “Forgotten.” If he wants to return to his original world, he'll have to recover his missing memories and complete the missions imposed upon him. But when fragments of his past begin returning, Heita discovers the image of a girl who looks exactly like Emma. What connection does she have to the life he's forgotten, and what exactly is Monty Paradise? In a mysterious world where the difference between remembering and forgetting can determine your fate, Heita must uncover the truth about his own past and decide whether the place he's been brought to is really a paradise at all.