Ouji's birthday approaches and his friends ask Kanade to help with preparations for a party to be held at her family's cupcake cafe. Kanade hopes to prepare him a load of cupcakes to be eaten with a 'lucky spoon'. She becomes downhearted when she overhears Ouji talking about a 'princess', which she assumes is his girlfriend, but Hibiki and Hummy manage to cheer her up. On the day of the party, Siren intercepts Ouji and casts a spell on him to make him fall asleep, only to be found in a dubious position when Hibiki and Kanade arrive. Siren creates a Negatone out of one of the lucky spoons, causing the PreCures to have bad luck. However, they manage to overcome their misfortune and defeat the Negatone. As Ouji wakes up, he shows a kind approach towards Siren, who runs off in embarrassment, before going to his party, where it's revealed his 'princess' was actually his pet dog.
王子先輩の誕生パーティを、ラッキースプーンで開くことになった。奏はとても張り切って、王子先輩のために最高のカップケーキを作るという。そして、みんなで盛り上げてすてきなパーティにしようとする。
