These are images of three deities with one halo, in the so-called Zenkoji Amitaba Trinity style, a style modeled after the style of the secret principal deity of Zenkoji Temple in Nagano. This style, where three deities are placed in front of one halo, is similar to the images of Tathagata and two followers, one of the Horyuji Kenno Homotsu (over 300 cultural properties offered by Horyuji Temple to the Imperial Family) possessed by the Tokyo National Museum. It is said that this trinity might have been influenced by the Buddhist images created in the Korean Peninsula during the Three Kingdom period (sixth to seventh century).
There is an inscription engraved on the back of the central deity, which says that these are in the Zenkoji Tathagata style where three deities are placed in front of one halo and that they were created in 1254 in Nasu, Shimonokoku (currently, Nasu in Tochigi prefecture) with Priest Saininas the promoter to collect contributions. The term "Chubabaku(鋳模)" in the inscription means that these are an imitation of the Zenkoji Amitaba Trinity.
Inscription on the back of the central deity