Switch On! 2011 (スイッチオン！2011 Suitchi On! Nisen-jūichi) is the fifth episode of Kamen Rider Zi-O. It is the first part of the Kamen Rider Fourze and Kamen Rider 555 tribute arcs. Thus, it features the return of Chuta Ohsugi, Daita Kondo, Chikao Nezu, Takumi Inui, and Masato Kusaka, portrayed by Takushi Tanaka, Kazuyoshi Nagazawa, Yuya Hara, Kento Handa, and Kohei Murakami respectively. It also features the debut of the Fourze Ridewatch, Zi-O FourzeArmor, Geiz BuildArmor and Time Jacker leader Swartz.
This episode is accompanied by the fifth episode of Kamen Rider Zi-O: Supplementary Plan web series, Sougo Tokiwa and the Mysterious Phone.
Geiz and Tsukuyomi investigate a case of young girls mysteriously disappearing from Amanogawa High School, and are confident that an Another Rider is involved. When their suspicions are proven true, they receive a handful of support from the school's Kamen Rider Club .