Ace barges into Yu and Grim's dorm late at night, wearing a strange collar. Following Yu's suggestion, they head to Heartslabyul House the next day, but a surprising encounter in the renowned rose garden thwarts their plans.

The residents of Heartslabyul House are growing increasingly unhappy with their housewarden's strict rule-abiding ways. Meanwhile, Ace must find a way to convince the housewarden to remove the collar around his neck.

Ace notices Riddle's happy mood as the perfectly prepared unbirthday party begins. Seeing this as his chance to get the awful collar removed, Ace approaches Riddle with the chestnut tart he baked. However, Riddle's unexpected reaction turns the situation from bad to worse.

Ace and Deuce's duel with Riddle becomes the catalyst that unleashes all the dissatisfaction of the other Heartslabyul residents. However, the unexpected backlash shocks Riddle so deeply that he begins to undergo an ominous change.

Riddle's magic begins to rampage along with the explosion of his emotions. Realizing the danger everyone is in, Headmage Crowley orders everyone to evacuate. However, Ace, Deuce, Yu, and Grim are determined to face Riddle and his raging magic.