Gentaro and his friends enter the third-year class headed by Mr. Ohsugi, and Gentaro tries to befriend new first-year students Haru and Ran. However, Haru is given a Zodiarts Switch by the Libra Zodiarts.

Gentaro and the Kamen Rider Club must figure out how to deal with Haru as the Musca Zodiarts and Mr. Ohsugi's discovery of the Rabbit Hatch, along with the latter's confiscation of the 38th Astroswitch.

While celebrating Kengo's birthday, the Horoscopes have located their final member, Pisces, in Ran Kuroki, who has been given the chance to study abroad in America. But after Leo attacks, Hayami gathers the Kamen Rider Club to tell them the truth of what has been happening and prevent Ran from becoming the final Horoscopes.

Ran refuses to give her Pisces Zodiarts Switch that will finalize Gamou's plans, so he sends Tatsugami to take her Switch. Elsewhere, Kengo discovers a secret from the USB drive he found in the late Emoto's office.

With Kengo's death at the hands of Sagittarius Nova and the destruction of the Rabbit Hatch, a distraught Kamen Rider Club reads the final letter from the Core Child written before his death. A resolved duo of Riders must face the Horoscopes one last time to avenge their fallen friend and stop the Day of Awakening for good.