Responses
Yakwoo said he was bit by dog, although his balls is like...gone(?) i wouldn't know how it works in men biology. But this is set in china (clothes, palace), where both organs are removed so I guess they trusted enough (by having a not fully developed penis and balls being bit off) especially if he only cared about cleaning and deemed him a coward at first.

If someone asks, I can explain further, but it'll come with a content warning. But, from what I know, it's interesting the author made Yakwoo a eunuch because by having a penis, he's technically not a eunuch, but maybe eunuchs in Korea are different from others.