Ho-on-ko is the annual memorial service for Shinran Shonin, the founder of the Shin Buddhist tradition. This service expresses our gratitude to Shinran for showing the Path of the Wisdom and Compassion that is Amida Buddha. The observance began after Shinran’s daughter, Kakushin-ni, carried on the administration of Shinran’s mausoleum, as did her descendants, who ultimately became the Monshu of the Hongwanji sect. (The Monshu in Jodo Shinshu Buddhism is the guardian of Shinran‘s mausoleum, as well as the head of the sect. As of June 2014, the current and 25th Monshu of the Nishi Hongwanji temple is His Eminence Sennyo Shōnin (Ōtani Kōjun, born 1977). He succeeded his father Sokunyo Shonin (Otani Koshin, born 1945).

Ho-on-ko is the principal holiday in which one participates in the art of “hearing the Light” through listening to Dharma talks, having discussions, participating in rituals and sharing the Sangha fellowship.

— Source: Midwest Buddhist Temple Jodo Shinshu Buddhism