Take Off (HINAI Natsuki)

From Shoujo-Sense:

While working as a monitor in the all-but-abandoned school library, first year Mei finds herself captivated by a mysterious boy with hair the colour of the setting sun. Never expecting to see him again, she's surprised when he shows up the next day, only to fall asleep and end up rushing out of the library suddenly and without a word... Who is he, and where does he go at the same time each day?