"No one man can defeat an army, but one creature can. How does such a creature come to be?" — Tayū
The episode opens with a puppet stage performance (in what appears to be a variation of Bunraku puppet theater), before what seems to be a high ranking and important audience. The narrator of the show says that no one man can defeat an army, but a creature can, and proposes to tell the audience how such a creature can come to be. The narrator then begins a story where in ancient times the master of a Rōnin was slaughtered by a rival clan whose crest was the phoenix, and how it caused "a storm to rise in his soul" as he swore vengeance. As the narrator says this, we get quick flash cuts between the ronin in the show and Mizu, who is facing down the Thousand Claws. As she looks at the Claws and Madam Kaji's murdered assistant, a hateful glare comes to Mizu's face.
Mizu cuts down the first few members of the Claws, causing some of the others to give each other nervous looks. That buys Mizu and the others time to retreat into the brothel and barricade the formidable door. Madam Kaji, Akemi, and the other girls retreat to a basement, Mizu sends Ringo to look after them and gives him a knife to use to defend himself and protect them. The girls shut themselves inside a room, with Ringo standing outside as a last line of defense. After a few moments, Akemi joins him, holding a tiny dagger, and declares the Claws will have to get through them both.
Upstairs, Mizu thinks about her childhood, remembering some tender moments with her mother, her mother's increasingly harsh admonishments against being seen, and forcefully shaving Mizu's head and telling her that she must always appear to be a boy, since the "bad men" are looking for a blue eyed girl. She then remembers her home burning down, the apparent death of her mother in the fire, and swearing to get revenge by killing the white men.
Her reverie is broken when the Claws finally manage to break down the door and enter the room. With most of the interior in darkness, they go to one of the few places with any light, and Mizu promptly ambushes them from the darkness, easily cutting them down without them even seeing her. After some time passes, a second small group comes inside, and Mizu manages to kill several more with the same tactic, but the leader of this bunch manages to fight back effectively, parrying her blade, grabbing ahold of Mizu, pinning her against the wall, and then stabbing her in the side with his claws.
The narrator from the puppet show tells of the ronin's vow to kill everyone who wears the phoenix crest and destroy their entire clan forever, but notes that the ronin would find the demon's path of revenge to be a difficult one. Mizu's flashbacks show her own difficulties in her early attempts to try to find the white men, as she is stabbed in the side by a group of opium dealers she tried to question. Badly wounded, Mizu staggered away from their hideout, weakly searching for help. Meanwhile in the performance, the ronin's violent quest for revenge has early success, but takes a toll on both the ronin's health and mind. The ronin becomes sick, and it seems likely he will die of disease without fulfilling his vow. Both the ronin and Mizu find unexpected salvation; Mizu comes across a group of prostitutes on a bridge and realizes one of them is her mother, who is surprised to see Mizu. After Mizu collapses, she takes Mizu to her home and treats her there. Meanwhile, the ailing ronin crosses paths with a woman who takes pity on him and brings him to her home and tends to him, allowing him to rest and recover.
Mizu breaks free of the Claw who wounded her and overcomes him, then staggers deeper into the brothel, alternating between fighting the Claws and retreating long enough to grab a quick rest. A pair of the Claws find the basement, and boast to Akemi and Ringo that the samurai is cornered upstairs. Ringo and Akemi manage to defend themselves and Akemi, fearing that Mizu cannot defeat the Claws alone, goes upstairs to see if she can help. Mizu continues racking up a formidable body count with the Claws, but the same one who wounded Mizu earlier manages to catch her by surprise, starts strangling her, and seems to be on the edge of killing Mizu when Akemi stabs him in the back. Hearing the sound of more Claws approaching, Akemi desperately tries to wake an unconscious Mizu.
In Mizu's past, she recovers from her wound but the money she had is soon taken by her mother to feed the older woman's opium addiction. Her mother claims to have a solution to their problems; a marriage to a disgraced samurai and horse tamer/trainer living in the mountains, who needs a wife to aid him around his house. Mizu is very opposed to the idea, but is emotionally blackmailed into accepting. Mizu meets and marries Mikio, and as time passes, the two slowly begin warming to each other, and despite some rough spots, it turns into genuine affection and eventually love.
In the performance the ronin initially intends to leave the woman after recovering his health, but the woman tries to convince him to stay, and the two fall in love, causing the ronin to set his vow of vengeance aside.
Mizu wakes up just in time to save Akemi from several of the Claws, then distracts the rest into chasing after her while Akemi flees back into the basement. Mizu draws them outside, but there are still more members of the Claws there, and they gang up on her. Unless she can find a way to change the tide of the fight (and quickly), things are looking grim for Mizu as the Claws attempt to finish her off.
In her past, Mizu opens up to Mikio. He seems intrigued when she says that the main thing she did during her childhood and adolescence was study swordsmanship as part of her quest for revenge, and asks her to have a sparring bout with him. Mizu becomes very... enthusiastic during the fight and insists on escalating things, unsheathing her sword, then mocking Mikio when he shows reluctance to do the same. Eventually she begins to trounce him, and the fight ends when (after a period of dodging all his strikes) she throws him to the ground, shoves a blade against his neck, and then forcefully kisses him. Mikio, however, does not react to this well, pushing her away and saying that Mizu really is a monster.
In the puppet theater, the ronin has been living happily with the woman and their child, but he learns a startling fact about his bride; that she is a member of the same clan with the phoenix crest that he swore to destroy. The bride pleads with him, saying that she exiled herself from her father's evil clan, and tries to win over the ronin, but a fit of rage comes over the samurai. Before the eyes of his horrified wife, he draws his sword and kills their child, then kills her as well. Rage and hatred takes over the wife's spirit, causing her to rise from death as an onryō, and she promptly slaughters him, before causing natural disasters to ravage the world around them due to her fury not being satisfied by just the ronin's death.
Mizu plans to make amends with Mikio, but learns from her mother (who is smoking opium again), that Mikio has left to deliver the horses he has tamed to his lord... including a particularly impressive specimen named Kai that Mizu helped Mikio tame and which Mikio had said would be Mizu's horse, rather than giving her to the lord. While Mikio is away, a group of armed men ride up, looking for Mizu, and reference the bounty on her. Mikio comes riding by on his horse, raising Mizu's hopes that he will aid her in fight off the attackers, but instead he rides away, leaving her to her fate. Heartbroken and enraged, Mizu lashes out at the men who came to kill her with all of her characteristic fury and skill, tearing them with apart with Mikio's naginata.
Shortly after Mizu finishes off her attackers, Mikio comes back, claiming that he had a moment of cowardice but decided to return and help Mizu. Mizu doesn't believe him, accusing him of having told the men where to find her. Mikio instead tries to put the blame on Mizu's mother, pointing out how she's been smoking opium again lately, and says that she got the money from informing on Mizu. The older woman claims that she had simply been prostituting herself again on the bridge. Mikio and Mizu's mother fight until he stabs her with a knife in his anger. He tries approaching Mizu again, but she cuts him short by killing him with a throwing dagger. With her heart poisoned by the terrible pain of betrayal and heartbreak, Mizu decides to resume her quest for vengeance against the white men.
In the present, Mizu breaks free of the Claws, then in between fighting them off, she takes off the weights on her arms and legs, connecting them to each other and her sword to turn it into a makeshift naginata. The Claws, who were already at a disadvantage thanks to the longer reach of Mizu's sword, have absolutely no chance to touch her now thanks to the added reach of her blade. She kills the remaining Claws until they're down to a few survivors who flee in terror. She then grabs boss Hamata and brings him to Madam Kaji so Kaji and her girls can get their own revenge on him.
An exhausted Mizu can barely keep from collapsing when the sound of approaching horses can be heard. It turns out that the horsemen are samurai in service to Lord Daichi (Akemi's father) who have come to find Akemi bring her home. Akemi tries to defy them, asking Mizu to fight on her behalf, but Mizu refuses and allows the samurai to take Akemi. Ringo is aghast at Mizu for not helping Akemi and tells Mizu off, complete with taking off the bell Mizu tied around him when he became her apprentice. Mizu, for her part, simply begins to slowly limp away, moving on to the next stage of her attempt to reach Fowler.
At the puppet performance, the narrator concludes the show, and it is revealed that the performance was done for the shogun and his guests. The shogun then asks Akemi what she thinks of the entertainment in Edo. Akemi replies that there is one thing in the show that she believes was inaccurate: She says she met an onryō once, and searched the creature's eyes for any sign of love, mercy, or goodness, and found none. As Akemi speaks, we get a close up of her face, showing her teeth have been blackened, indicating that her engagement to the shogun's younger son has gone forward.
