It was your turn to train the kamaboko squad. You were doing the Rapid Movement training. You were someone calm so they thought your training would be too..

In the end it was not like that at all..

Tanjiro : “that wasn't so bad" He said smiling but he was lying

Zenitsu : “UGH..MY LEGS HURT SO MUCH"

Inosuke : “YOU ARE SO WEAK MONITSU" He said when he was clearly also out of breath

The other two, Kanao and Genya, were gasping for air. Meanwhile nezuko was perfectly fine.