Complex sentence: To everyone, Goemon looks like he's about to cut down Tokugawa, and Sasuke, who joined Tokugawa's army as a foot soldier, intervened by stabbing Goemon through his torso.
Split into simpler sentences: To everyone, Goemon looks like he's about to cut down Tokugawa. Sasuke (he joined Tokugawa's army as a foot soldier) intervened by stabbing Goemon through his torso.