Your style is really cute! I think I can work with this.
Here's my pitch: The young man is going to the magic academy as you say, but this academy is basically mage boot camp. The exercises are strenuous and the young man is having trouble keeping up. Faced with the prospect of failing out, he decides to earn himself some extra credit by taking down a vampire. The plot twist happens, and he learns this vampire is also a mage.
Then we learn why this mage is dressing up like a bat: She comes from a foreign land, where vampires and mages have learned to get along through a system of voluntary blood donation. She has come here to try and convince the people that there's a better way. Neither the vampires nor the mages, however, are interested in giving up their way of life.
Skeptical that vampires and mages could ever really get along, the young man nonetheless agrees to help out. The road to peace is a dangerous one, however, as they'll have to fight people on both sides to stop them from destroying each other. along the way they grow closer together and start to form a relationship as they fight to change the world.