Enzo knew all about Harper's imaginary friend Luca. He knew about what a good climber he was and how much he liked pizza. He knew how interested he was in the stuff Harper learned about in school and the way he told Harper stories about living in the walls. He even knew that his favorite color was green and that he didn't let Harper touch him.

But what Enzo didn't know was that Luca was real. Not until this week, that is.

It started out as a pretty ordinary week. Between his full time job as a personal trainer at a climbing gym, taking care of Harper, and his online college courses, Enzo was busy, as usual.

But he liked it that way. He couldn't remember a time in his life when he didn't work hard. Ever since their parents' death seven years ago, it had just been Enzo and Harper. They had been in and out of foster homes those first three years, with Enzo desperately doing everything he could to ensure they stayed together.

As soon as he turned 18 and graduated high school, Enzo applied to foster Harper himself until he could legally adopt his baby brother at 21.

Now 22 and 7, they had been in this tiny apartment for the last four years. "Luca" had appeared sometime during that period, maybe when Harper was five or six.

It wasn't that unusual for a kid to have an imaginary friend, so Enzo never thought too much of it. By Harper's accounts, Luca was apparently a tiny little man who lived in their walls.

"He's around your age, Enz," Harper had told him. "And he lives by himself, so he's pretty lonely. I accidentally saw him on the bookshelf one day, and that's why he visits me. He said he thought about leaving, but as long as I promised not to touch him, he said he would stay."

"That's cool, Harps," Enzo had responded, both impressed by Harper's creativity and wondering what the appearance of this imaginary friend meant. "Can I meet him?"

Harper had just shaken his little head. "No, he's too shy. But he said I can tell you about him."

And that's what Harper did. He didn't have much to say at first, as he apparently didn't see Luca that often. But after a while "Luca" became Harper's regular visitor, even earning the title of "best friend" from Harper.

It was pretty cute, actually, and Enzo liked hearing Harper's funny little stories about Luca at the end of each day when he tucked his brother into bed.

"Today, he let me time him as he climbed the bookcase!" he'd say. Or, "Luca says the neighbors are fighting again." Or even, "Luca likes that's you're growing your hair out."

And Enzo would always smile and say "really?" or "that's cool, Harps" or, "tell Luca to come say hi to me next time."

And that's all there was to it. Until this week.

***

On Tuesday, Enzo watched as Harper marched into the tiny bedroom they shared, lugging the ingredients for yet another "tea party" with the elusive Luca. It was really just pieces of Harper's after school snack, which he always tore down to size. Based on the crumbs Harper always had, Luca must be very small indeed.

"Whatcha got for him today, Harps?" Enzo asked, amused.

"Hawaiian punch and a bagel," came the resolute answer. "And a grape. Luca likes grapes."

Enzo waved him off. "Alright. Carry on. Tell Luca I said hi."

Harper disappeared into the bedroom. Enzo never bothered him during his little tea parties with "Luca." Harper always said that Luca ran away whenever he heard Enzo walking towards the room, so Enzo just stopped interrupting Harper during this play time.

Before Enzo had learned this, however, Harper would get mad at him for barging into the middle of snack time. "Get out, Enz!" he'd always say, pushing his big brother out the door. "You're scaring Luca! It takes him forever to come back out once you leave!"

Enzo always wondered if he should feel miffed about being kicked out of his own room by a seven-year-old and a tiny, imaginary man. But whatever made "Luca" (and by extension, Harper) happy was fine with him.

***

"So, how's Luca today?" Enzo asked later that night as he tucked Harper in to bed.

"He's good." Harper yawned. "He wants to meet you, but he's shy."

"Hmm?" Enzo mused, brushing Harper's light hair out of his eyes. Harper had mentioned a few times that "Luca" wanted to meet him, but nothing ever came of it. "Why's that?"

"He thinks you won't like him. Cause he's different."

Hmm, I wonder what that means, Enzo thought, thinking back to the parenting books he read to try to learn more about kids and their imaginary friends. Maybe a part of Harper is worried about my disapproval of something? And this is how he's trying to process and explain it?

"Different... how? Because he's small?"

"Yeah. He's scared you'll hurt him. Or won't let him leave. Or that you will make him leave. I don't know. He's worried about a lot of things. Just yesterday, he was worried about that cockroach before you squashed it. He was glad you took care of it. He says cockroaches are the worst. They get in his food supply and fight him for it. And they're gross."

"Umm, ok," Enzo didn't really know how else to respond to that. It was times like these when he'd wonder if Luca was imaginary after all. Harper always spoke about him so convincingly, like he was a real person. And the conversations they had about Luca were so darn specific.

Harper was creative, but Enzo didn't think he was that imaginative. And he was always consistent about the details about Luca over the past two years. Surely it would be impossible to remember every little detail about a fake person.

But... Luca couldn't be real. Tiny people didn't exist.

***

Enzo picked up Harper later than usual on Thursday, and Harper immediately burst through the front door as soon as Enzo unlocked it.

"Luca will think I forgot about him!" Harper yelled. He started kicking off his shoes frantically, and Enzo brushed past him to head into the kitchen.

"Don't forget to put your stuff away before you go play," he reminded his brother over his shoulder. "I'll go get your snack."

Harper didn't answer, too busy taking off his school things and making what sounded like a mad dash for their bedroom. Enzo heard the clatter from his place in the kitchen, and he paused in making Harper's sandwich.

"You better not be making a mess," he called to his little brother. Only silence.

Enzo finished the sandwich and put it on a plate, poking his head out of the kitchen to investigate. Despite Enzo's warnings, Harper had left his backpack and lunch kit strewn across the entryway. Enzo picked them up with a sigh, heading towards their bedroom.

"Harps," he complained. "How many times have I told you? You need to hang up your backpack and then wash out your lunch kit before you go play, remember?"

He stopped in the doorway and froze.

Sitting on the floor across from Harper was a little doll with dark hair that Enzo had never seen before.

He frowned at it. I don't remember getting Harper a doll or action figure like that, he thought. Did someone from school let him borrow it?

But then the figure leapt to its feet, eyes widening, and dove under the bed.

"Enzo!" Harper exclaimed, turning around to face his brother. "What are you doing here? You scared Luca!"

"I..." Enzo was speechless, overwhelmed by what he had just seen. He didn't know what to think.

"Was that... was that a... real person?" he finally got out.

"Yes!" Harper looked exasperated. "That was Luca, and you just scared him." He scooted across the floor and leaned down to look under the bed.

"Luca," he called. "It's ok. You don't have to be scared. Enzo won't be mean."

He shot his brother a glare. "Right?"

"Umm, right," Enzo breathed, still standing shellshocked by the door.

Harper kept talking, trying to comfort whatever little creature was now hiding under the bed. Enzo shook his head to clear it, walking forward to crouch by the bed next to Harper.

Peering into the gloom, he could just see the shadowy figure of... of Harper's... friend. Luca.

From what he could tell, it was a male figure, around his own age. The little thing's eyes were wide and locked onto Enzo. They stared at each other, spellbound, until Harper nudged Enzo.

"Enz!" he complained. "Back up. You're still scaring him. Let me do the talking."

Enzo blinked but complied, sitting up and scooting back. Harper kept talking quietly, his voice so low that Enzo couldn't really hear him. But whatever he said seemed to do the trick, as after a few minutes, Harper scooted back, and the little figure crept out from under the bed after him.

Enzo just sat there and gaped until Harper pinched him.

Be nice, he mouthed at his older brother, and Enzo nodded once. Now out in the open like this, Enzo finally got a good look at the tiny man. And he... really wasn't at all what Enzo was expecting.

The little man's dark brown hair was messy, his eyes light and wary. Though small, he was clearly fit, and he kept one hand on a sheath that Enzo assumed held a knife of some sort. His clothing was worn and patched in some places, a large bag slung over his shoulder.

"Luca, this is Enzo, my big brother," Harper introduced, seemingly oblivious to the tension in his little friend's body. "Enzo, this is my friend, Luca."

"You're real," Enzo breathed, and Luca backed up a little.

"Umm, yeah," the little guy said hesitantly. "Last I checked, anyway."

Enzo whipped his head around to stare at Harper. "He's been real this whole time?" he demanded. "And you didn't tell me?"

"I did tell you!" Harper argued back. "So many times! I didn't know that you didn't believe me! That's your own fault!"

"Yeah, but it's just... most kids have imaginary friends," Enzo defended himself weakly. "And I've never seen a tiny person before, so what else was I supposed to think?"

Luca watched the ping pong argument with wide eyes. Finally, the little man chuckled, and both Enzo and Harper fell silent to look at him.

He held up both hands. "Umm, it looks like you guys have some stuff to sort out," he said. His face looked a lot more relaxed now that Enzo hadn't made any moves to reach for him.

Luca looked at Enzo next. "I... I can come back later to properly introduce myself," he offered. "And to answer any questions you have." He bit his lip, the nervousness back in his eyes. "I'm sure you have a lot."

"No, wait, you can't leave, Luca!" Harper burst out, and the little man's eyes shifted to him. "You didn't even get to eat yet!"

Luca just shook his head, and Enzo stared, mesmerized, to see such familiar, human actions on such a small scale.

"I still have the Oreo and goldfish cracker you gave me yesterday," he said. "I'll be fine."

"Ok." Harper looked crestfallen, but to Enzo's surprise, he didn't argue. "Bye, Luca."

As Enzo watched, the tiny man waved and headed towards the bookshelf, glancing over his shoulder every now and then as if to make sure no one would grab him

Enzo vaguely wondered if he should do something to stop this mysterious person from leaving, but Luca had promised to come back. And Harper had said over the years that he wasn't allowed to touch Luca, so maybe the little man would disappear if a human touched him? Enzo had no idea.

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A/N: Aaaaannnnd here we have human Enzo and Harper and borrower Luca! This extra has a total of 5 parts, so enjoy watching the role reversal unfold! Don't forget to vote and comment and see you in the next part!