A past Kamen Rider has lost his memories, next time on Kamen Rider Zi-O episode 4.
Episode 4: No Continue 2016
Writer: Kento Shimoyama
Director: Shojiro Nakazawa
Genius Gamer M reveals himself to be Emu Hojo, who transforms into Kamen Rider Ex-Aid. After the Another Rider revives, the others learn that Emu as Ex-Aid has lost his memory. Sougo pleads for Emu to assist them but is met with callous attitude.
Source: Kamen Rider Official