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.

The heat and humidity of the rainy season make it difficult for the DIY club to get any work done, so Kurei invites everyone to her house for air conditioning. When Serufu and the others visit Kurei’s room, they discover a surprising side to her.

Midterms are over. The parts for the secret hideout have been ordered. Kurei has announced that they’ll start building on Monday. Serufu asks everyone to come to her house on Sunday, before building starts, so that she can show them something.

The DIY club suffers a massive shock. Devastated, they head home without beginning the construction of their secret hideout. When Purin hears what happened from Jobko, she digs out an old keepsake and goes to see Serufu.

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.

The DIY club holds a celebration at their newly completed secret hideout. Then summer vacation starts and Jobko heads home, promising she’ll see everyone again. Purin takes Serufu to the DIY club, saying that the secret base is still missing something.