A female assassin and a lieutenant in the Mugai-ryū. Hyakurin was the wife of an abusive samurai, Hayakawa Kakōsai Genkei, who was obsessed with trying to gain fame by training Matsuhiko, their sickly son, to become a strong swordsman. She later kills her husband to avenge the death of her son by his father's hand and is then arrested and sentenced to death. Her case came to the attention of Kagimura who subsequently recruited her into Mugai-ryū. Hyakurin's most unusual physical trait is her blonde hair (concealed frequently under a wig), which she maintains by bleaching it with a strong chemical as a compulsive desire to remove bloodstains from it. While her skills with a sword are unremarkable, she has an extensive knowledge of poisons. This knowledge carries over into her choice of weaponry, a collapsible wrist mounted crossbow with poisoned bolts named Burafuma (Little Steps). The crossbow also possesses two blades such that when the weapon is collapsed, Hyakurin can use it to stab her opponents. After volume 11, Beasts, her skills are impeded after having her arm broken. She later becomes pregnant and ends up "retired" from the Mugai-ryū because a deal between Habaki and Giichi when Giichi earns his freedom. She has no desire to keep the child because she believes she will be reminded of Shinriji's death and the faces of the Ittō-ryū men who raped her. She first appears in Dark Shadows part 1.