You were walking around town till you got kidnapped by demons, the demons threw you into a plywood shipping crate and the demons locked the door. But a couple minutes later the demons threw Rengoku and Tanjiro in the plywood shipping crate with you. Causing Tanjiro to fall on top of you

Tanjiro: OW- my poor head-

Tanjiro rubs the back of his head

Rengoku: Who is there!?