Although the rounin Souichirou Senou quickly discovers that most of his new neighbors in the Katagi Apartments do not trust him, his childlike wonder at the world around him allows him to strike up a friendship with the carpenter's son, Kankichi. With Kankichi's help, Souichirou begins to establish a life in Edo's tenements and exchanges his longtime sword Kunifusa for a bamboo blade, due to his newfound desire to refrain from violence.

Unfortunately for Souichirou, avoiding conflict in Edo is not always possible. Before long, Souichirou finds himself stalked by the brutal assassin Shinnosuke Kikuchi, who delights in butchering anyone caught between him and his target. Each time Souichirou must step forward to defend himself or the people of the tenements, he reawakens the intense bloodlust of his younger days and resurrects memories he would much rather forget.