One morning, on her way to school, carefree, daydreaming Yua Serufu wrecks her bike and an upperclassman comes to her rescue—a chance encounter which sends her down a path to answer the question, "What does 'DIY' mean?"

The DIY club needs more members to stay open. As Serufu wonders just how to do that, her classmate Hikage Takumi offers a thought—“If you made the club room cuter, then maybe other students would take an interest…?”

The DIY club decides to go to the beach. They’ll gather materials to make little things like bracelets to sell, adding to their club funds. When Purin hears that Jobko is going to the beach, she decides to go along, unaware that it’s a DIY club activity.

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.