Tanjiro ventures to the south-southeast where he encounters a cowardly young man named Zenitsu Agatsuma. He is a fellow survivor from Final Selection and his sparrow asks Tanjiro to help keep him in line.
Tropes associated with Tsuzumi Mansion Arc:
- Alas, Poor Villain: Kyogai, despite eating countless humans dies happily as Tanjiro appreciated his writing style and techniques.
- Arc Villain: Kyogai, a former member of the Twelve Kizuki, who's trying reclaim back Muzan's good favor and return back to the group.
- Asshole Victim: Kyogai's father, who belittled his son's writing and denied his talents, is one of the few humans in the series who deserved getting killed by a Demon.
- Crippling Overspecialisation: Zenitsu can only perform the first form of Thunder Breathing.
- Crouching Moron, Hidden Badass: Zenitsu, while sleeping killed the Tongue Demon, despite acting extremely cowardly and asking his clients to save him.
- Disappointed in You: Muzan to Kyogai when the latter hits his limit of gaining power by consuming humans.
- Due to the Dead: Tanjiro, Zenitsu and the survivors perform a small ceremony for the deceased at Tsuzumi Mansion.
- Elemental Motifs: The Thunder Breathing Style used by Zenitsu mimics lightning, allowing for swift strikes and movements akin to lightning ripping through the sky.
- Hot-Blooded: Inosuke Hashibira.
- Oh, Crap!: The Tongue Demon, seconds before getting killed by Zenitsu.
- Living Macguffin: Kiyoshi, a Marechi whose blood is 100 times more potent than an average human's, probably due to a rare blood type. Kyogai targeted him to boost his rankings in the Twelve Kizuki, and Tanjiro gives him an amulet from which he can suppress his blood potential from other Demons.
- Pet the Dog: Zenitsu despite being shit-scared by Demons, gives his all to protect Nezuko's casket getting opened in broad daylight by Inosuke and takes several beatings from him to honor Tanjiro's request.
- Muzan simply expelled Kyogai from the Twelve Kizuki in his backstory instead of killing him. Considering how much of a Bad Boss he is, this is surprisingly merciful of Muzan to do.
- Reverse Psychology: Tanjiro ends up doing this unintentionally twice with Inosuke:
- When Inosuke refuses to help bury the dead because he wants to finish his fight with Tanjiro, the latter mistakenly assumes that Inosuke is too injured to help and offers to let him rest while everyone else does the work. Inosuke, feeling patronized, angrily decides to participate in the burial, declaring he can bury more bodies than anyone else.
- When Inosuke tries to goad Tanjiro into fighting him by stealing his food, Tanjiro once again misinterprets it and offer his food to Inosuke, thinking he's that hungry. Inosuke refuses and starts eating his own food again.
