Steve
None of the Avengers knew what to think of the kid. He woke them up in the middle of the night more often than not, terrible screams echoing down the hall. In the five days he'd been training with them, none of them could really think of how to train him any better than he already was. The kid was like a well trained soldier. It mostly turned into conditioning, cleaning up techniques and learning from each other; not unlike how it had been for the Avengers before the kid had joined them in the tower.
They caught glimpses of a bright, funny, personality under the sullen and quiet shell, but none of them understood why he was so miserable. He vanished at least once a day without trace, coming back hours later and clearly upset; one of the few times he showed true emotion. Steve often would return from his morning run to find him in the gym going over well practiced movements he couldn't define. Spinning, advancing, retreating. He looked deadly and serious.
They'd quickly learned to not ask him about the names he'd sometimes yell out in his sleep. Those questions often resulted in the kid either vanishing for several hours or going to the gym and beating the shit out of his hands. They all took turns stopping him after a couple hours, bandaging bloody knuckles and making sure he actually goes to bed, or eats or whatever it was they worried he'd forgotten to do that day. Just like they all did for each other on their own respective bad days. Steve worried about how frequent Percy's bad days were.
Today had been a good day, for all of them. They were lounging in the living room, while Tony stood in the other room ordering pizza. Percy came in quietly carrying a duffle bag and looked at the group.
"Is there a pool around here?" He asked. It was one of the few times the kid had shown genuine interest in something at the tower. He doesn't watch TV, hadn't bothered with the XBox, something Steve had been informed everyone liked to play nowadays, and whenever Steve caught a glimpse of Percy not eating, sleeping or working out, he was often staring at overturned photo frames or reading from a book that was definitely not in English. Percy didn't even seem that interested in the words, but would often trace a finger over the images of the buildings inside it, or over the cramped notes that filled the margins.
Steve nodded.
"I'll show you." Percy nodded his thanks and followed Steve into the elevator. He was almost used to Percy visibly tensing in the elevator. Steve wondered what could have caused such a strong aversion to the machine.
When Percy saw the large swimming pool, his face broke out into a large childish grin. All exhaustion vanished from his face, and true happiness radiated out from his face. It made Steve smile to see. Dropping everything Percy dove right in with hardly a splash. Steve stayed in the doorway, curious about the kid. But when he didn't resurface after a minute he started to get worried. After it started to get close to two minutes he started towards the pool. He looked frantically around the water when suddenly two hands shoved him from behind. Steve slipped and plunged into the water. When he resurfaced the rest of the team was there, laughing. Steve growled playfully, pulling his sopping wet t shirt off and chucking it at Tony. Then he jerked back with fear. He'd nearly forgotten that Percy was somewhere under water, and hadn't surfaced for several minutes. He started to turn in the water when the kid in question turned up behind Tony, pushing the man into the water. It quickly became a free for all, everyone pushing and splashing and fighting in the water.
By the end of the day, Steve could see a marked difference in Percy. The day in the pool had been really good for the newest member of Steve's family.