Kamen Rider OOO 10th: Core Medal Resurrection which is released on March 12th 2022 will get a two-episode spin-off that will be released the following day. The episode will be as follows and take place chronologically the day before the movie:
Core Medal Resurrection/Introduction – Eiji Hino returns after years of wandering in search for a way to revive Ankh. He is reunited with Hina Izumi. While Eiji was absent, Hina is fighting the revived Greeed with Chiyoko Shiraishi. Appearing in this episode are: Shu Watanabe as Eiji Hino/Kamen Rider OOO, Riho Takada as Hina Izumi, Marie Kai as Chiyoko Shiraishi, and Taito Hashimoto as Kazari.
Birth X Birth/Introduction – Chairman Kougami has developed “something” to combat Ancient OOO and the Greeed. He gives Gotou a box filled with Core Medals. This will give birth to Kamen Rider Birth X! Appearing in this episode are: Asaya Kimijima as Shintaro Gotou/Kamen Rider Birth X, Hiroaki Iwanaga as Akira Date/Kamen Rider Birth, Mayuko Arisue as Erika Satonaka, and Takashi Ukaji as Kousei Kougami. Both episodes are narrated by series narrator Jouji Nakata.
The news was broken by The Toei Tokusatsu Fan Club (TTFC):
— 東映特撮ファンクラブ（TTFC） (@tokusatsu_fc) January 22, 2022