After his moms death, to protect himself, young Jitae introduced himself as Hajoon to Mieum cause he was scared that Mieum was hired by Suryeon to spy on him. He was relieved when he didnt find anything about Mieum at Suryeon desk. But then got info that Mieum might still be associated w her because Mieum was with his mom the day she got murdered. (see chap 31, Hajoon was also there and dropped his name tag which Mieum hold onto) Plus he got kidnapped by Mieums dad that make him doubt Mieum even more.
Basically, it's a huge misunderstanding. Mieum really did care for Jitae but Jitae felt betrayed/ doubtful cause all of the things that happened. (￣∇￣")
Recap anyone? Im so confused right now ○_○