Hanasaku Iroha: Home Sweet Home Movie [Underwater]

Ohana has grown accustomed to living in the hot springs inn her grandmother manages, Kissuisou. One day, the daughter of a manager for Kissuisou's rival inn, Yuina, comes to Kissuisou for training to become a landlady herself. As Ohana is observing her training, she finds "a certain item" in the storeroom while cleaning.