There is a prayer of Shorou-nagashi in the last day of Ura-bon-e. In this prayer, Busshists pour special water called Akasui(閼伽水) onto a paper Buddhism tablet called Kami-ihai, in order to cleanse ancestor's worldly desires and impurity.
Shorou-nagashi is a ceremony conducted at the last day of Higan-kuyo
or Ura-bon-e, in which people release an ancestor's paper tablet to rivers
or the ocean, and it also represents seeing off ancestors' souls to where
they belonged, the place of Dainichi-Nyorai.