The Tale of Nokdu S01 E12 Yul-Mu's True Color

"Mischievous gisaeng in training has a suspicious mother."

After the widows of Muweol Corps left for Hanyang to kill the local functionary, Nok-Du and Lady Cheon find out that the widows are in a trap. Lady Cheon asks Nok-Du to go help out the widows, and that's how Nok-Du becomes a member of Muweol Corps.