Brief Summary of Undercover Princess:

Kim Jonghyun was a cocky prince that never had to work. He was lazy and he had a quick temper. However, that all changed when he met you, Shim _____. You are the daughter of the two top spies in SM Agency. Your first mission was to go undercover as a princess in order to protect Jonghyun's twin sister, Haneul. This was a problem. You're a tomboy, the exact opposite of what a princess should be like. During the time you spent at the Kim household, you fell in love with Jonghyun. You also fought U-KISS, from the rival NH Agency,  alongside SHINee and defeated them. After the battle with U-KISS was finished, Jonghyun came back with you to SM Agency to become a spy.

Now:

Your parents have put you in charge of Jonghyun's training. You must train him quickly so he can join SHINee. However this isn't an easy task. Not only is Jonghyun lazy, he also has no experience in fighting or stealth. Turning your boyfriend into a top spy could be your hardest mission yet.