Vivild, a catastrophe-class demon with immense power, lurks among the living...and anyone and everyone is a suspect! As their target is a master of disguise, the Book Burners can't be too careful in their search, but who can be trusted? Obviously, there's only one way to find out--hitting the water park?! The revealing swimsuits should make it harder to hide any demonic seals, but they also seem awfully convenient for Mitsunari, who's having trouble hiding his impure gaze...