you snuck to the training grounds, to secretly watch the male hashira train

they didn't notice you... yet

Iguro: he's slashing a watermelon with his katana

Rengoku: he's chatting with Uzui

Uzui: he's drinking water, and listening to Rengoku

Sanemi: he's showing off his scars to Giyuu

Giyuu: he's trying to ignore Sanemi