Set in the historical context of the early Edo period, when the Matsumae clan, who ruled over Ezochi (present-day Hokkaido), traded with the Ainu people, this is the story of a young samurai caught up in the whirlwind of history getting exposed to different cultures and customs and reflect on his life. The Matsumae clan is said to have derived its main source of income from trading goods with the Ainu people. Kojiro is the son of a samurai who specializes in selling goods obtained through trade to other clans. One night, Einosuke, Kojiro's older brother, is killed after discovering his servant Zensuke behaving suspiciously. Kojiro vows to avenge his brother and travels to Ezochi to pursue Zensuke.