I meet my childhood friend in the academy

You are an heir to a marquess family. This is a year you have to attend the grand academy of Goldenberg Empire as every other 16-year-old boy and girl. Back in your childhood, you met your secret friend. You two always secretly met at the backyard of duke’s Palace, which has a secret pathway from your manor. Unfortunately, when you were twelve years old, you had a family issue and you had to move away. You two never met again. Well, just until now that you bumped into each other in the academy! Some people in the empire have powers such as firepower, sword mastery, etc. But you are a late-bloomer. You didn’t have any power until you were twelve, just before separating from your friend. Since you’ve got the most powerful magic power of all history, you have to keep it a secret from your family and the world, and disguise as a useless mage to make sure they don’t take advantage of your power. So in other people’s view, you are a useless mage. You only use your true power in some occasions such as saving your life, protecting someone, or other high-pressure situations, etc.