Tanjiro Kamado and Nezuko Kamado vs Shrine Demon

Tanjiro Kamado and Nezuko Kamado vs Shrine Demon was a short skirmish that occurred north north-west of the Demon Slayer Corps headquarters. It concerns the Demon Slayer Tanjiro Kamado, the recognized demon Nezuko Kamado and a spider-like demon hiding in a mountain shrine.

Prologue
Following the death of Kyojuro Rengoku, Tanjiro, along with Zenitsu Agatsuma and Inosuke Hashibira became intensely motivated to train harder and become stronger than ever before. While doing chores in the Butterfly Mansion, he was tasked with killing a demon that had inhabited a mountain shrine. With Nezuko now a recognized Demon Slayer, the siblings set out to their mission.

Battle
Amidst pouring rain, Tanjiro arrives to the shrine where it has been reported, with Nezuko inside her box on his back. As he looks around, the demon crawls up to the ceiling unnoticed. He then detects a scent from above and looks up to see the demon descending to attack him, drawing his blade in response. It crashes to the floor and chases him, while Tanjiro sprints up a pillar. Nezuko emerges from her box and claws at the demon's legs. Together, they drive the demon out of the shrine through a wall and force it out into the open; Nezuko leaps up and tries to punch the demon, narrowly missing. The Shrine Demon flees and descends the mountain, while the siblings pursue it.

Tanjiro realizes he has made a mistake when he sees the demon is heading to a village at the mountain's foot. The demon hides in a tool shed and heals its leg, while trying to rationalize what kind of Demon Slayer his assailant was. Tanjiro appears at the shed's entrance and asks the demon resign himself for his death. The demon refuses and charges at him once more. As it gets close, he uses Water Breathing, Fourth Form: Striking Tide, slicing off the demon's legs, before turning around and cutting through its neck to kill it.

Some time later, a young boy who has heard the scuffle runs to the shed with a flashlight. He shines it around and looks for something but cannot, despite knowing he had heard something.

Trivia

 * In the manga, Tanjiro is only shown returning to the Butterfly Mansion from a solitary mission, while the anime expands upon this with the addition of Nezuko and a short battle shown.