It has been several decades since dungeons appeared on Earth and monsters began to run rampant all over the world. Due to the contamination of magical power caused by the appearance of dungeons, people gained powers called skills, but the age of adventurers as in a fairy tale never came, and many towns were abandoned, the economy declined, and the world was filled with lawless areas slowly heading towards extinction. In a ruined town where death is always close by, Amano Mamoru has continued to hone his skills, together with a mysterious beautiful girl named Shizuku, with whom he shares the same fate through the skill "Remaining Lives", with his unique skill "Equivalent Exchange Store" as a weapon, he challenges the world to coexist with dungeons——!!