On June 2, 2008, Toei announced on its various official websites that there would be a series of short five-minute internet movies that are spin-offs of both The King of Hell Castle and Boom Boom! Bang Bang! GekijōBang!! to be accessed by a mobile phone service. In the case of The King of Hell Castle, the featurettes are called
Net Edition: Kamen Rider Backwards-Kiva: The Queen of Hell Castle (ネット版 仮面ライダー裏キバ 魔界城の女王). The internet films are set to be released on July 11, 2008.