Kazumi Sawatari, known as Kamen Rider Grease Blizzard, is a key character in Kamen Rider Build. Originally the leader of the Hokuto Three Crows, Kazumi is a passionate and loyal fighter who becomes an ally to Sento Kiryu, the protagonist. Driven by strong convictions and a deep sense of camaraderie, Kazumi ultimately sacrifices himself in a heroic act, using the Grease Blizzard Knuckle. His journey is marked by personal growth, friendship, and a willingness to put others before himself.