jiminasha I can think of quite a few tomboy FLs, but I haven't seen My Girl. Can you give some more detail about what you mean when you say you want the ML to be naive? Naive in the sense that he's sheltered and doesn't know much about life? Naive in the sense that he doesn't have romantic experience? Are you looking for a ML that's kind and innocent, or more a ML that isn't particularly smart / talented / successful?
Yoona's Street (2014) the FL is a tomboy. She is a pickpocket who doesn't back down from a fight who meets a guy who is studying for the civil service exam.