Conner:
Alas, poor Conner. Orphaned shortly after birth, he spent the first decade of his life at an orphanage. Contrary to the stereotypical hellish orphan homes, Conner lived a good life there. He was fed well, was never abused and was shaping out just fine. He did come from a far richer neighborhood than Tessa, so much of his life experience has been quite different.
Similarly to Tessa, however, he was bullied for most of his life. He had his friends here and there, but he generally stuck by himself. When he did get into interactions, he showed more emotion than he probably should have, and was a frequent target of bullies. He eventually learned to stick up for himself, and was left alone then on.
And then came The Day; that dreadful Day. Conner remembered it perfectly. A group of men with robber masks entered the orphanage, and threatened the head of the home. Conner still remembers one of the masked men, in a muffled voice, saying
"Get the children out. Every single one of them."
42 children stood in front of the gunmen. One of men pointed a gun at a brunette girl and a red headed boy. The head of the home reluctantly shoved them forward. The other gunmen pulled body bags onto them, lifted them and walked off.
The other one looked like he was about to leave. Then he saw Conner. The man grabbed him and shoved him into another bag. For good measure, the gunman shot the head of the home as he walked off with Conner. 
When Conner was released from the bag, he was immediately stabbed in the arm with a doctor's needle. He fell asleep, almost instantly. When he woke up, he found himself in the place he would stay for the next 6 years of his life: A tiny (very tiny) closed cage, with a single breathing hole poked at the top. 
Conner didn't realize what happened until dinner that night. A gigantic hand, the size of a skyscraper, opened the cage and dropped a few breadcrumbs in. This was Conner's life. He received one meal every two days, until this fateful day. 
Luckily for Conner, a woman who happened to be a teacher, was dropped into the cage with him a few months later. She was a math professor at a college, but she tried to teach Conner everything she could. This would be the only reason that Conner could act at a 16-year old level at age 16.

 At the very least, he wasn't treated poorly in the cage. Well, he wasn't treated like anything, really. The black market couldn't care less about treating him one way or another. He could wake up at any time he wanted, and really do anything he wanted within the cage.
Conner's day started like any other. He woke up, Ms. Thompson already preparing a lesson for him. If he were not locked in a cage, never to escape, he would object. But he had nothing else to do, so... dare I say it? Learning was fun!
Conner just stared at the wall, waiting for Ms. Thompson to finish writing math problems on the inside of the cage. That's another thing. Whoever dropped in food had graciously provided them with a tiny pen, at Ms. Thompson's request. Sometimes, they'd even get a little shred of paper. 
Conner was pondering how strange the cagekeeper must be. He/She willingly worked at a black market operation, but was kind enough to treat their slaves well. Very strange.
"Ahem"
That's Ms. Thompson. She pointed at a math problem she wrote on the wall of the cage. Conner had to kneel down and concentrate in order to read the dark text. 
"Uh... 18. Right?"
Ms. Thompson stared at it for a second.
"That's right!"
This was generally how he would spend most of his day. He could get so bored, that he would often do this every day of the week. Conner had no idea what day it was anymore. However, he knew that if he worked every day, then he worked on weekends. That wasn't right.
When he wasn't attending Ms. Thompson's classes, he would think. He treasured the time he had alone, just to think about things. He wondered what the world was like now. Maybe everything was different. 
He thought about oceans and clouds and rainbows and such. He wondered if he would ever see the Sun again. Sometimes, he wondered if he even remembered the feelings that people often hold dear.
Could he still feel the blades of grass between his toes? Could he still remember the warmth of the Sun? Could he still remember the taste of a delicious meal? 
Above all, however, Conner wondered what would happen once he was chosen. No one in charge of the operation had ever explained what would happen to Conner. He knew what he knew thanks to Ms. Thompson and his own ability to think about things.
This was a black-market operation that shrunk people down and put them in cages. He knew that much. But they were obviously spending money to feed him. Thus, as he learned, something has to be paying for that. Eventually, he learned that he would be sold one day. Someone would choose him, and he would belong to them. He would be their pet human.
Conner thought about all of the different kinds of people he knew before The Day. There were friendly people, rude people, happy people, sad people, empathetic people and sadistic people. Well, the sadistic people were the ones who put him here.
Conner sincerely hoped that the person that should choose him would just be someone looking for a tiny friend. He liked the idea of that. He imagined being lifted into the air, staring deep into the night. 
He was perfectly fine with not being returned to normal size, as long as he had a good life. Also, he really, really, really hoped his chooser was female.
Conner didn't know it, but today was the day. In the middle of Ms. Thompson's lesson, Conner's cage door was opened. He was carefully injected with a tiny needle. Ms. Thompson was screaming.
Conner, however, was more optimistic. In his remaining moments of consciousness, he smiled, and thought about how different his life would be when he woke up. Eyelids shutting quickly, he looked at Ms. Thompson.
"Bye," he said.