Zenitsu Agatsuma vs Tongue Demon was a battle that took place in the Drum House. It focuses on the battle between Demon Slayer Zenitsu Agatsuma, against the Tongue Demon.
Prologue
At first, Zenitsu and Shoichi were finding a way to get out the Drum House. While telling off Shoichi for making loud noises, Zenitsu noticed a demon behind his back. Both him and Shoichi ran away from the demon but eventually, they got into a room with the Tongue Demon.
Battle
Zenitsu falls asleep and Shoichi is shocked to discover this. The Tongue Demon approaches slowly and Shoichi screams for Zenitsu to wake up. The Tongue Demon extends his tongue to attack him before Zenitsu slices his tongue off quickly. Zenitsu stands up and protects Shoichi before he gets into the stance for the first form of Thunder breathing. The Demon notes that he's giving off a different presence. Zenitsu then uses the Thunder Breathing: First Form - Thunderclap and Flash to kill the Demon.
Aftermath
Zenitsu then wakes up and he is surprised the Demon is dead and thinks Shoichi killed it.