Korean names only have 2 - 3 syllables, the first one always containing their last name which is in our mc’s name is Kim. Also Korean alphabet is extremely straight forward. Mu is one syllable with a single character for each letter and for Heun, it exactly has three characters from the korean alphabet, ‘h’ and ‘eu’ which is considered a single letter or basically you treat it as another type of vowel and ‘n’ . So you read it as Kim Moo Hhun.
Heun and Hun sounds different, hun is like a Hooon and heun is like when saying the un in undetermined. Yeah yeah

how do you pronounce muheun? "moo-hoon" or 'moo-hyoon" ?