Blood & Shadow; My F-ranked Shadow Ability Has an Unlimited Skill Sets

Following the world's greatest catastrophe—which nearly led to the apocalypse—the revelation of the skills to utilize magic and supernatural powers were brought to light. They, who were chosen by the stones were called the Ability Holders.
With the globe entering a new era, an Academy specializing and entirely dictated for ability users was established. At this academy, abilities are evaluated and ranked based on how they influence the world.
Gleren Stasis, a F-rank student at this academy—due to a certain circumstances—was forced to covertly work for an organization that preserves global harmony and balance; a pacifist and a nonchalant boy who would rather idle his days watching anime and play games than to do anything bothersome.
However, one day with the arrival of Maria, the vampire princess—his wishful and peaceful days came crashing down.
Maria as the Last Vampire was a special existence for which she was constantly sought after by her enemies. With such danger always lurking about the Vampire Princess, Gleren Stasis—a F-ranked student at Saint Stella Academy—was tasked with protecting her at all costs without disclosing the truth about himself(?).
Will his life thoroughly change—or will he be the one to change the life of the vampire princess?
This story revolves around the life of an underwhelming boy and the one's he had sworn to protect.