A girl is living with her husband in an underground district due to deadly monsters taking over the surface. Her husband is a soldier who is called to go outside the gates to check some traps that might have caught one of the monsters. They have been together for like 13 years and have a very deep relationship. He promised to come back and tell her something but he ends up dying on this mission. She receives his wedding ring as proof of his death. She ends up finding out he might not be dead after reading a book that seems to describe their reality and tells how to escape the district. But people see her with the book so she has to escape. She takes their mutual friend with her. Then discovers that this world is a video game. And finds her husband has been reborn (?) as the lord of the monsters who killed him. She promised to never leave him and he feels strangely attracted to her (without having any memories). She gets him to leave with her and tell him not to kill anyone.