Zenitsu Agatsuma vs Tongue Demon

Zenitsu Agatsuma vs Tongue Demon was a battle that takes place in the Tsuzumi Mansion. It focuses on the confrontation between the Demon Slayer Zenitsu Agatsuma and one of the three demons inside the mansion.

Prologue
As they walk around the halls of the mansion, a nervous and wary Zenitsu continues to hold onto Shoichi's hand as the duo attempt to find a way out. Calling out to Zenitsu, only to be told off by the latter for making a loud noise, Shoichi then tells Zenitsu how he feels unsafe around him, especially considering how frightened Zenitsu was. Zenitsu begins to profusely apologize and tell him that they should stay quiet to avoid being attacked by demons, just as the Tongue Demon appears in front of them.

Zenitsu, now much more terrified than before, desperately tells the demon to stay back, additionally saying that saying neither he nor Shoichi would taste good as they begin to run away. The demon simply responds by saying that he would not know how they would taste if he did not try, proceeding to chase and attack them.

After running into a room, Zenitsu collapses onto the ground out of sheer fear, telling Shoichi to escape and leave him. The young boy of the two on the other hand immediately refuses and Zenitsu is further pressured with his responsibility to save Shoichi. As the Tongue Demon approaches them, he tells them that he is going to suck their brains out through their ears. Zenitsu suddenly passes out due to both his fear and the stress of the current situation finally catching up to him. Shoichi begs him to wake up just as the demon lashes out its tongue.

Battle
An unexpected gesture occurs as the demon's tongue is cut off by Zenitsu as the latter stands with his head hung low; subconscious sustaining him. Moving into the stance for using Thunder Breathing, First Form: Thunderclap and Flash, Zenitsu gets ready to decapitate the Tongue Demon without hesitation. With one swift move and a direct slice from Zenitsu's Nichirin Sword, the demon's head now lies on the ground, as Zenitsu easily goes through with his attack, now standing victorious against the demon in battle.

Aftermath
Shoichi gapes in shock while he looks at Zenitsu who wakes up and screams at the sight of the deceased demon's head, now decapitated from its body. The confused Demon Slayer misunderstands the situation and begins to express extreme gratitude towards Shoichi for "saving" the pair, also telling him he should have let possessed extreme strength much earlier on. Shoichi, now at a loss for words and decides not to say anything, telling Zenitsu they should go.