In Kamen Rider 555 20th: Paradise Regained, Smart Brain, which has evolved from a governmental organization into a company with the goal of eradicating all Orphnoch life, is now under the leadership of Kitazaki.

To prevent the extinction of the Orphnochs, Masato Kusaka fights against Smart Brain's enforcer, Reina Kurumi, who is assisted by Takumi Inui who had disappeared years ago but has now returned as Kamen Rider NEXT Faiz, taking a lead role within Smart Brain.

Mari and her group find themselvesbewildered as they come under attack by the newly arrived Faiz. What drives Takumi to join forces with Smart Brain, and what has he been up to during his absence? This tumultuous reunion sets the stage for a fresh narrative that intertwines the fates of Orphnochs and humanity.