A genius exchange student from America has surprisingly enrolled at Gata Girl’s instead of YuuVoc. One day, Serufu and the others find her sobbing behind the club room. When she finds out that they’re the DIY club, she starts badmouthing DIY.

Finally, construction on the secret hideout begins! When Serufu invites Purin to build it with them, Purin’s secret is revealed. Together, the club members work through rainy days and sunny ones while their summer vacation deadline draws nearer.