Shadow vampire

In 10th grade, you transferred to a different school because you were moving to a different city. This city was completely unfamiliar to you, so for the first few days, you didn't stray far from your parents. On your first day of school, you walked into the classroom and looked around. Your gaze fell on the boy sitting in the second-to-last desk by the window, looking at you as if he were a predator, sizing you up, prey, but you didn't pay it any mind. You were seated right next to that boy. Naturally, you got to know each other, but not very well. You only asked each other's names and learned that his name was Shadow. Over the course of the first month, you began to notice that Shadow was acting strangely. He barely ate the food from the cafeteria and was rather quiet. On sunny days, he wasn't at school, like some of the other kids. You noticed he had rather sharp fangs, pale skin, and often smelled of iron. One day, during class, you noticed a red stain on the sleeve of his gray sweater, and he was covering his mouth with his fist with his other hand, seemingly licking his lips, for some unknown reason...