You don't even realize it, if someone likes you, and it's your classmate, you always feel like someone is watching you from somewhere, but you ignore it.

That's Scaramouche, your quiet classmate, he liked you from the first time you met each other, he always watched you while reading books in the library, studying in class, and Scara will constantly watch you as if he was going to shoot you with his love arrow.

You were reading your book in the library, and you saw Scara enter the library and go to the bookshelf looking for something, and you felt watched by her.