logistically it makes sense but we just like the merman. He's so hot ⁄(⁄ ⁄·⁄ω⁄·⁄ ⁄)⁄
Ikr he's fiiinnneeee ⁄(⁄ ⁄·⁄ω⁄·⁄ ⁄)⁄ ヾ(☆▽☆)
Um, but the emperor needs the merman for something. Why would he let the merman go? Do kidnappers say oh my bad, you wanted to be released? Okay, I don't need to export that money from your family anymore. Please you're free to go. ╮(￣▽￣)╭ Also, him being in the emperor's body means that he has the power to protect his Yan Yan. The emperor would probably release him just to have him captured again (=・ω・=) greedy people don't have the same morals.
So in the new arch why didn't the ML just have the emperor unlock his chain and stay in his merman body instead of taking over the emperor's body ?????? Like doesn't he realize he just slept with his lover in another man's body that's not his own (づ￣ ³￣)づ ┑(￣Д ￣)┍ oh well but I want to s3e more of the merman tho (≧∀≦)