When a group of Japanese high school students embarks on a school trip to Europe led by their unconventional teacher, Suomi, they find themselves in for a unique experience. Their journey takes an unexpected turn when Suomi brings them to a nudist beach, where strict rules are in place. To prevent any untoward incidents, Suomi instructs the male students to refrain from having erections. She pairs them with female students to help manage any potential issues. Surprisingly, it is the class president, Naotatsu Nagato, who struggles to abide by this rule. As his classmates rally to assist him, hidden feelings and confessions come to light, setting the stage for unexpected revelations and emotional connections.