Sento Kiryu Male A genius physicist who transforms into Kamen Rider Build. However, he can be a bit airheaded. For some reason, he seems cold toward Ryuga. Do not make him speak in a feminine manner.

Ryuga Banjo Male A former fighter and a total muscle-head, the polar opposite of Sento. He is often insulted by Misora as a "muscle-brained idiot" and tries to argue back. Do not make his personality overly violent.

Misora Isurugi Female The true identity of the net idol "Mi-tan." Usually downbeat but a reliable older sister figure. She seems particularly skilled at keeping Ryuga in check. Ensure her first-person pronoun is "I" (Watashi) and not "Boku."

Soichi Isurugi Male Misora's father and the man who took Sento in. He is pathologically good-natured and runs a cafe.