One day, a large hole suddenly opened in the garden of my house. There, there was a mysterious slime with a trembling metallic body.Yuma Mitaka, a dull high school student, ends up spending his days exterminating the "metal slime" that for some reason springs up in the hole every morning... but as he repeats this every day, Yuma's body has undergone an amazing evolution! ! An unprecedented unparalleled fantasy that begins with an ordinary day!