会社内でファミリーデーのイベントを実施することになり、3部の仕切りに任命された璃子(与田祐希)。しかし、イベント全体を仕切る大石(中島歩)が納得する企画を考えられずにいた。そんな中、真司(望月歩)の机の下にあったプラモデルで盛り上がっていたところを社長に見られ、あるプラモデルを使用したイベントをやる流れに。準備をする璃子たちは、イベント前日にリハーサルを兼ねて前夜祭をすることに…!
Riko (Yoda Yuki) is assigned to organize a family day event within the company, and is assigned to divide the 3 divisions. However, she couldn't come up with a plan that would satisfy Oishi (Nakajima Ayumu), who was in charge of the entire event. Meanwhile, the president sees that Shinji (Ayumu Mochizuki) is having a lot of fun with a plastic model under his desk, and they decide to hold an event using a certain plastic model. Riko and the others are preparing for the event, and on the day before the event, they have a rehearsal and an eve...!