The synopsis for this manga seems to be translated incorrectly, as the main character was always a woman. She just used to be mistaken for a man because she was tall and handsome.
As for the story, I really like it! Not only is there some interesting mystery around Sila/Roel's new family, the Demon King shows a lot of personality in the first chapter and there also seems to be more to him than meets the eye. I can't wait to see him again! The romance between Sila and Jullius is just adorable. They're both a little airheaded, and don't see any problems with things like sharing food. It's refreshing to see a couple that isn't easily embarrassed and skirting around each other.
All in all, wkile it doesn't do anything groundbreaking, I'd really recommend it to fans of the genre! I promise you'll have a good time!