One day, the tax office receives a phone call. It was an accusation call that the inn where Nanao works as the proprietress had evaded a considerable amount of tax. Immediately, Oiwa and Inoue, tax officials, headed to the hot spring inn where Nanao was staying to conduct an undercover investigation. When Nanao notices that an employee is going undercover while staying overnight at a hot spring, she plans to somehow avoid a tax investigation by playing a super dangerous erotic trick on the employee in a see-through yukata.
