"I really really really want to stay. I'll be so careful with the books - I'll write you copies if you want -"

Blink. "Uh, you're just not supposed to be on the premises."

"Yes, you said, and I assumed the reason for the rule was concern for the books. What is the reason for that rule."

"...I just work here, kid. Shoo and I won't tell anybody I caught you here."

" -okay." He puts the book back. He vaults the balcony and goes to somewhere else in the stacks.

The janitor lets out a strangled yelp when he jumps.

Well, the janitor is the one who told him to shoo. He pays enough attention to things which aren't his book that he can notice anyone getting close and flee to a different shelf before they bother him.

The janitor has concluded that he's a cape and is going to call the Parahuman Response Team.

Well that's not good. What is wrong with these stupid horrible people. He leaves the library and goes a ways off and listens for the locking people up people to arrive.

The PRT tell the janitor that being in a library after hours and knowing parkour is not something to call them over.

Oh good. 

So the janitor calls his supervisor, who says she'll call campus security.

This place has endless layers of locking-people-up, doesn't it. He should have taken a book but what if it got wet or something. He curls up and sings to himself and waits for this lot.

Campus security comes and prowls the stacks and doesn't find him and leaves.

Once they have left he climbs around the outside and forces a window and goes back in and goes back to reading.

It's dark but not pitch black so he can probably do that fine. In the morning the library opens again.

He pays enough attention to people to avoid them entirely. Towards the end of the day he is thirsty; he finds a corner and rebraids his hair so from a distance it might look like he mutilated himself like these people and then he goes out into the better-trafficked areas and witnesses a water fountain and drinks delightedly.

Drinking from water fountains: acceptable behavior that does not inspire anyone to try locking him up.

Oh good. Food is more of a problem. He goes outside and tries some of the trees and they are not at all tasty or very nutritious.

"Are you eating leaves," says a girl with a book.

"I am hungry and I have been advised to get a job but I thought I could just eat the leaves instead. These leaves are terrible so maybe I will get a job."

"...they're leaves. Like, off trees. You can't eat them."

"Where I'm from you can. You can here too but the nutrient value is really disappointing."

"They don't have nutrition facts on them they're just leaves. What's wrong with you?"

"I can obviously tell what I'm getting out of food I have eaten. Nothing is wrong with me, something is wrong with this place."