Baekhyun didn’t notice it at first. There was nothing suspicious about that particular student. As far as he knew, the student was simply one of the hundreds and thousands in their university who frequented the library where he worked part-time. There was absolutely nothing suspicious at all. Yet as days, weeks, and months passed, he finally noticed something.

The student would always arrive in the library at the same time - always a quarter to five in the afternoon.

He would always sit on the same seat at the same table - always the one near the corner by the windows.

He would always have a book in his hands - always studying earnestly and seriously.

He would always leave at the same time too - always ten minutes before closing time.

But the strangest thing of them all, he would always wear a face mask - always the same black horrid mask covered half of his face.

And this got Baekhyun quite interested to know more.