While on a mission with Rangiku to fight sword beasts, Haineko encounters one named Narunosuke, whose master was a coward, and who went with the others in order to become stronger. Haineko becomes friends with Narunosuke, sneaking him food and medicine despite the belief that the sword beasts inevitably lose control of themselves. As feared, Narunosuke gradually does lose control of his mind and body, and Rangiku arrives to deal with him. Haineko tries to stop her, but when Narunosuke becomes too dangerous, she is ultimately forced to destroy him.