Returning home from school one day, Rikuo finds a group of yōkai eating expensive pastries. At first he accuses his grandfather of having stolen them, but he is told that they were a gift from the visiting Yakushi Clan yōkai Zen. Rikuo peeks into a large open room to see an angry-looking Zen seated and waiting. They exchange a cheerful greeting, as it has been a fair number of years since they last saw each other, and Rikuo wonders why Zen is at the main house. Yuki Onna, Nattō Kozō and several unnamed yōkai watch from the doorway, wondering aloud the very same thing until Rikuo tells them to be quiet and apologizes for how lively things are. Meanwhile, Yuki Onna decides to usurp another yōkai's job of bringing tea in, but trips and spills the contents of both cups on Rikuo. Zen explodes at her, threatens to kill her for harming his sworn brother, and then just as quickly settles back into his seat and smiles while asking Rikuo what sort of pranks he's pulled lately. They then have a disagreement as a result of Rikuo wanting to live a human life and Zen being disgusted by the former's attitude toward becoming the Third. Their argument sends Zen into such a fury that he launches his poisonous feathers and makes to leave - stopped only by the excitement causing him to cough up blood. Everyone makes a frantic attempt to help him.
After Zen has left, Karasu Tengu explains to Rikuo how the yōkai of the Yakushi Clan have weak bodies, and Rikuo shouts at his grandfather, declaring that Nurarihyon talked Zen into coming in order to preach about becoming the Third. When Rikuo calls it a cruel tactic because of Zen's weak constitution, Nurarihyon gets annoyed and leaves - but Rikuo doesn't end his tirade against the Nura Clan and its supposed purpose. Karasu Tengu spreads out a map of the Nura Clan's territory and teaches Rikuo about the inner workings of the group, and how its true purpose is to protect the large number of weak yōkai beneath the Nura group's banner.
Meanwhile, Hebidayu, an anthropomorphic snake yōkai traveling with Zen, tries to console the latter by declaring they don't need the Nura Clan's power. Zen admits that he doesn't have much life left, and says he is happy that at least the last bit could be used for the Nura Clan's sake - all the while, he remembers when he and Rikuo interacted as children and how different Rikuo was compared to the present. The pair arrive at the Yakushi Clan's headquarters, and a cluster of shadowy forms are seen conversing about it being the perfect time to eliminate Zen.
Back at the Nura Clan main house, Aotabō and Kurotabō have found a bottle of expensive sake which turns out to be Rikuo's. Taking the bottle back, Rikuo declares his intention to go apologize and properly explain himself to Zen. He and Karasu Tengu board Oboro-guruma and head for the Yakushi Clan's headquarters... where a building has exploded into flames. The fire is Hebidayu's handiwork, and Zen draws his sword in fury at the betrayal - but he is immediately struck by another coughing fit. While Zen is immobilized, his former subordinate attacks. Overhead, Rikuo and Karasu Tengu can see the flames and immediately intervene to find Zen on the floor, leaning against his sword. Hebidayu recognizes Rikuo as the supposed third heir and decides this is an excellent opportunity to kill two birds with one stone. Unfortunately, when he launches an attack at the pair, Rikuo in his "night" form intercepts and slices Hebidayu in half with Nenekirimaru. Zen is confused, having never seen Rikuo's "night" form before, but Karasu Tengu is in awe to have seen Rikuo awaken again. Together, they explain the situation to Zen, who says that in this form, Rikuo could easily become the Third. Rikuo offers him the bottle of sake, and Zen asks if they can exchange sakazuki in order to become Rikuo's true sworn brother, rather than just a hand-me-down from their parents. Rikuo agrees, saying he'll protect Zen, and they drink. Karasu Tengu muses on how the council members would surely understand if they could only see this version of Rikuo.
Riding back to the main house, Rikuo's "night" form asks how many sakazuki he needs to exchange before other yōkai will accept him/his "day" form as the third heir. He then declares that he will become the next head of the Nura Clan, and Karasu Tengu wonders as to the drastic difference between what Rikuo is saying now and what he had said that afternoon in his "day" form.