Urashima saves a turtle and gets invited to the Ryūgū-jō, where, to the dismay of Urashima, the princess Otohime despised him and gave him the lowest quality service possible - just to overload his brain to the breaking point.
助けたカメに連れられて竜宮城に来てみれば、質素なもてなしと、とんでもない土産を持たされてしまった。