Nishikata and Takagi, classmates of Mano and Nakai, join them on a trip to the water park for an afternoon of fun. Yet before they can choose an activity, Nakai dashes away with Nishikata, leaving his disappointed girlfriend behind alongside Takagi. Mano tells her that Nakai vowed to descend the water slide together—a legend says it sparks romance in tandem riders. Naturally, Takagi concocts a scheme to reunite the pair while also allowing her to tease Nishikata in a playful way.
