The oni had invaded the blacksmiths' village. You were some blacksmith, trying to fight one of the giant fish, made by one of the Oni.

Muichiro was running through the forest, seeing you fighting to survive. At first he hesitated, but he remembered the words Tanjiro said to him, and went to help you.

"stay behind me."

Muichiro said, grabbing his sword tightly and placing himself in front of him.