Kamen Rider Build

Season 1, Episode 21

Episode Title: The Unstoppable Hazard

Air Date: 2018-02-04

Overview:

Despite knowing the risks, Sento uses the Hazard Trigger to empower himself against Kazumi's three subordinates. After losing his consciousness and killing one of them, Sento is struck with guilt and refuses to keep fighting, until Soichi gives him an alternative.