Two princes from neighboring realms—Richard of the Custard Kingdom and the protagonist of Sablé—have maintained a spirited competitive bond since childhood, their contests typically ending in stalemate or narrow margins, with Richard consistently dominating their fencing matches. When word arrives that the tyrannical King Delarin has seized the Mille-Feuille Kingdom and imprisoned the princess Tiramisu, Richard seizes the opportunity to outshine his rival once more, commandeering a boat and setting sail before the Sablé prince can react. The ensuing chase leads both princes, along with newfound allies, into a mysterious curse that transforms them into frogs—a peculiar affliction that somehow holds the key to uncovering the dark secrets festering within the conquered realm.