There's something about Loki.
Thor's always been fascinated by his younger sibling, who always seemed to be immersed in a world so different from his own. Loki's world was a mesmerising alien realm, full of musty tomes, unearthly colours and wild magic.
He doesn't understand it, but that doesn't stop Thor from tailing Loki whenever Loki sweeps heavy books up in the small cradle of his arms, huffing for breath as he carries them all to the library, stubborn and sure.
Loki is to Thor as night is to day, he muses; where Thor is loud and rambunctious, Loki can often lapse into silence like the grave, green eyes sharp and never missing anything through the shifting summers. Thor fights and spars the golden days of Asgard away while Loki thumbs through books after books of seiðr, learning breathtaking new spells he occasionally demonstrates to Thor when he flatters bookish Loki into showing off for him.
Thor is a little envious, sometimes, of Loki's grasp of magic. He'd held his brother's hands, once, brushing his fingers over that warmth as Loki'd taken a breath and conjured darkness in front of him. Thor'd almost leapt back, startled, but Loki had gripped his hands tightly so that he couldn't budge. Closing his eyes, Loki chanted words unfamiliar to Thor, and tiny lights had flickered to life, painting a miniature version of the stars and Yggdrasil before his eyes.
Loki had always been a wary, guarded sort, but Thor would never forget the way his cheeks had flushed with pleasure and pride when Thor'd told him that his seiðr was the most beautiful thing he had ever seen in all the Nine Realms.
(Eventually, Loki would brush off Thor's cajoling and begin to guard his magic jealously instead, very much like how he would hide a secret lover away. Thor enjoyed whatever Loki would deign to share with him while it lasted.)
Thor smiles, recalling little moments past, and then straightens abruptly when Loki takes another two tomes off the shelf to a table, and sits down. Loki looks rather enchanting like this when he's poring over his books, rather like the small, dark-haired nymphs Thor's seen in the forests.
He tiptoes carefully behind a bigger shelf, grinning to himself. Loki is brilliant, and remarkably clever. He's very proud of his younger brother and his mastery of magic, but Thor reckons Loki needs some time away from his books to have some fun once in a while.
Thor peeks from behind a book that's almost as thick as his head, checking to see if Loki's still bent over the table in thought.
Thor attempts to move behind Loki as stealthily as he can, until he's right behind his chair. He leans closer until he can almost read the letters on the pages, and reaches out a hand to tap Loki's shoulder—
"A surprise attack? How unoriginal, Thor."
He doesn't shout, but it's a near thing. The illusion in front of him falls apart at his touch, and Thor whips around to glare at Loki accusingly. "You tricked me!"
Loki just smiles mysteriously, eyes dancing. "I certainly didn't. I'd spotted you following me to the library a few times now, and I wanted to see what you'd do."
Thor sulks a little. "I just wanted to whisk you away from your books for a bit, Loki. Let's go out for a while, get you out in the sunshine."
"I have to study," Loki taps Thor's nose, and Thor blows a raspberry at him. "But if you missed my company so that you had to tail me for days in order to muster up the courage to actually ask me to spend time with you…"
Squirming away from Loki as Loki moves to ruffle his hair, Thor sputters indignantly. "That's, I didn't have to muster up my courage or anything! Such lies you spout from your mouth, Loki. I, I just—"
"Whatever you say, Thor," Loki cuts him off with a smirk, and pushes him to the floor so that Thor's sprawled in a tangled heap of curses and limbs. "I'll race you to the Hall."
Thor can only stare dumbly from the ground as Loki runs out of the library, laughing all the way.