John
From the reaction Wally showed, Hugh slowed down. He didn't mean to scare the kid. He wanted to apologize but he wasn't really good at admitting things... Especially to someone he just met. "Just don't... Sneak up to me next time. I thought you were some kind of bad guy, sheesh." His words are a bit harsh but he didn't mean it to hurt. That's when he noticed the Gallade. If there's anything that could cut, it'll definitely be that Pokémon. Clicking his tongue, he turns from Wally, still feeling bad—enough to make his face ugly. Yes, the guy isn't good at expressing himself. 

Actually, Wally could be the first person he met on this island that isn't someone of his region. It's actually... More nerve wracking. There's some comfort to have someone hailing from his region. Even if he doesn't know them all. "What are you doing here anyway? All the way out of town- are you training too? That Gallade of yours looks tough. It's getting me fired up-" Then he noticed that necklace around Wally's neck. "WHAT—what is that?!" He abruptly got close to the other. "Is that a mega stone I've heard about!"
Michael
"R-right", he took a dry gulp, before trying compose himself once again. Once he felt a little more comfortable around the Unova boy, Wally feel his muscles relaxing. Even his heartbeat started to go at a more steady rhythm. "Wait... I don't look like a bad guy!", he squeaked, knowing that his appearance and stature was far from villainous. If anything, Hugh seemed to fit the description of a bad guy. 

Although he met people from many other regions, Wally always felt a little uneasy around new people. Of course, being around Gallade made him feel more secure. If his Pokemon didn't strike the spiky haired trainer, it wasn't good to jump into conclusions. "What am I doing here...? I usually take walks outside, but I was actually knew that their was some secret area like this here!", the short teen sheepishly chuckled before scratching the back of his head. "Ga!", even Gallade felt gushed with the praise! "Yeah! It's a mega stone! I got this one from my older sister!", Wally held onto his necklace and showed off the rainbow colored stone.
John
Crossing his arms, he close his eyes. "I'm not someone who judges people based on their looks." Although he may have said that just to sound cool. "Wait, you have a knack for finding secret areas?" That's actually a useful ability. Hugh wondered if Wally was with him back then, things would've been easier. Oh what the hell, he's always sticking in the past. Why... Back to the present, Hugh was fanboying over that stone. "That's really lucky of you. Then that means... Your Gallade mega evolves?"

Ever since he started studying about mega stones during his look for imports in Kalos, Hugh has been interested. But none of his Pokémon could mega evolve anyway. "You must be a very strong trainer to have something like that. Tell me, how far did you get in the league?" He closes the space between him and Wally every time he asks, getting partly crazy even if it's just him interested. "How do you use it? Can you use any mega stone on any Pokémon that can mega evolve?" His eyes are now bloodshot. "Huh? What's the deal!"