According to the history of Hongan-ji Temple and the origin of Koraku-ji Temple (Shinonoi Shiozaki, Nagano Prefecture), Saibutsu is identified with Yukinaga (or Michihiro) UNNO, the son of Yukichika UNNO, who was descended from the Shigeno clan, a famous clan in Shinano Province.
この西仏は、本願寺の歴史や康楽寺（長野県篠ノ井塩崎）の縁起によると、信濃国の名族滋野氏の流れを汲む海野幸親の息子で海野幸長（または通広）とされている。