Teppei, after years of training under the enigmatic Karen, heads to a scientific conference to reunite with his brother Kotaro Takamiya. However, his familial hopes are shattered when a ruthless woman named Aramis massacres the attendees to abduct Kotaro. In his quest to rescue his brother, Teppei stumbles upon a dilapidated mechanical steed, B't X, which springs back to life through Teppei's blood, becoming his loyal companion in the battle against the enigmatic Machine Empire.