The Black Bulls were ordered by the Wizard King to investigate the devils. Yami takes Asta and Nero and goes to talk to Captain Charlotte of the Blue Rose Knights, since she has experience with forbidden magic and curses. But when they get there, Charlotte suddenly runs off somewhere and they're all in shock. Charlotte had memories of while Charla took over her body and fears that Yami had found out her true feelings and she ended up panicking. But then, she makes a decision.

Thanks to Gordon's father, Asta and the others were able to find out that there might be clues surrounding the devils in the Heart Kingdom and manage to get permission to enter the kingdom due to the fact that Mimosa had gone there previously to study overbroad. Asta, Noelle, Finral, Mimosa and Nero head to the Heart Kingdom. Asta and the others initially enjoy their trip there, but something that Langris told Finral had been bugging Finral. Suddenly, Asta and the others are faced with a rather unexpected trial. Will Asta and the other Black Bulls be able to obtain information on the devils?!