Manatsu and Sango discuss on what clubs to join, during which, Laura suggests making one themselves. As the two human girls do research for their own club at the school's library, they encounter a stoic bespectacled girl, Minori Ichinose, who does not believe in the existence of mermaids although she likes mermaid stories. Deciding to find out more about that girl, Sango and Manatsu discover that she is a top student in school. However, when they try to compliment her on a story she wrote, Minori, believing otherwise, turns down their praises, due to a past traumatic experience back when she was in the school's literature club. The next day, Minori meets Sango and Manatsu at an exhibition at the city's museum, and encounters Laura for the first time. Despite the others' encouragement, Minori timidly tries to back off. At that moment, a sea slug-like general of the Witch of Procrastination, Numeri, summons a Yaraneeda to terrorize the museum's courtyard. Manatsu and Sango transform to engage the monster only for the enemy to overwhelm them. Encouraged by Laura, Minori finally resolves to believe in herself. As a result, the third Tropical Pact grants Minori the power to become Cure Papaya who defeats the Yaraneeda with assistance from her friends. Afterwards, Minori, having broken her limits, befriends the trio.