Kaisei Mogami, also known as Kamen Rider Metal Build, is a character introduced in the Kamen Rider Build universe. He is an alternate version of the main protagonist, Sento Kiryu, hailing from a parallel world. Metal Build is recognized for his ruthlessness, intelligence, and scientific prowess, making him a formidable and morally ambiguous adversary. He plays a crucial role in the Build New World: Kamen Rider Grease V-Cinema, challenging the established protagonists and adding layers of complexity to the series' narrative.