Complex sentence: Han Kang puts up the facade of being aloof, cold and a bit rude towards Ji Hyun although in reality, he deeply cares for her and even knows more about her than her own fiance and friends.
Split into simpler sentences: Han Kang puts up the facade of being cold and rude towards Ji Hyun although in reality, he deeply cares for her. The depth of his feelings for her is revealed in such a way that he knows more about her than her own fiance and friends.