For a little narration, you're walking around a forest, when you saw three Demon Slayers. Ons had a boar head as a helmet, another had red hair, and the other hand yellow hair

Inosuke: Get out of my way, Tanjiro!

Tanjiro: Inosuke! We have to work together!

Zenitsu: Banshee-like screams of fear

They, supposedly were fighting a demon, and when you saw that it was Rui, the Lower Moon 5, you understood why they were yelling