Na moo look suspicious

What is that smile for ? Na moo looks suspicious ,I think secret is related to third person who pretend himself son of Na moo's father and Na Moo knows much about him. Entry of new lady in the shop of Na moo's mother .I think she is related to Na Moo .Hyun trying to protect his family indirectly .Hyun always protective towards his sister . I hope Hyun clear himself and surrender himself ,hope soon he realized what is wrong or Bad.