(You’re Tanjiro and this is when you get affected by Enmu’s demon blood art).

You were on a mission with Rengoku, Zenitsu, Inosuke and Nezuko on a train. Enmu attacked and put everyone, including you guys under his blood demon art, sleeping basically.

In your dream (or nightmare) you everything is black and red, you then see your youngest brother, Rokuta (who’s dead) and he’s crying, he finally speaks.

Rokuta: “Why didn’t you save us??? We needed you, brother!!” He says while crying.