After fighting for hundreds of years, humans and vampires signed an armistice agreement with their noses pinched. Only vampires diagnosed with human diseases can obtain permission to enter the human world.
What is a "human disease"?
That is, a special disease that can only sustain life by sucking the blood of a loved one. It is usually detected before the vampire matures and breaks out after the mature period.
Unfortunately, I contracted a human disease and was sent to a mixed school with humans before I matured. My elders saw that I was going to die.
What's even more unfortunate is that the humans in mixed schools are all weird guys.
Purpose: love and life