Thanks to Gordon's father, Asta and the others have discovered that there may be a devil's clue to the “Heart Kingdom”. With the cooperation of Mimosa, who had previously studied in the Heart Kingdom, Asta received an entry permit. Five people, Finral, Mimosa, and Nero in the shape of a bird, decided to head to the Heart Kingdom. Asta and his friends enjoy their trips, but one of them, Finral, was bothered by what his younger brother, Langilles, pointed out before he left!? An unexpected trial awaits them. Can Asta and the others get the information of the devil safely?!