Nataehan Doryeongeul Wihan Gyoseup

Worried about his son Bi-Young living like a ne'er-do-well, Lord Bae asks Jin, the capital's top assassin and errand boy, to discipline his son. Sneaking into Bi-Young's bedroom for the mission, Jin unexpectedly witnesses him masturbating. His playful side kicks in, and he teases the terrified Bi-Young.

“I'll do anything you want...”

Young master, when you cry with such a pretty face, it makes me want to give you a proper scolding.

(Source: Ridibooks, translated)