Having learned of Mitsunari Ishida's taking up arms, Ieyasu Tokugawa decides to march his massive army to take him on at Sekigahara. Nobuyuki Sanada, who had parted with his brother Yukimura in the lead-up to this event, would have to join the fray as part of a unit separate from Ieyasu's, and under the control of his son Hidetada.
