The first unit captain of the Shinsengumi. He is deceptively delicate-looking and has an overall sunny disposition that occasionally borders on childishness, but displays frighteningly deadly skill in combat situations. He shares a strong bond with Hijikata and is also one of the only people who has a deep understanding of Tetsu. He takes Tetsu seriously and often practices with him. In addition, Souji loves children and is rarely seen without his piglet Saizo when he is off-duty. Souji is later diagnosed with tuberculosis.