Over the next 10 days Kai spent roughly 3 years practicing and studying. He figured out he was right about running on air. If he just flew he was nowhere near as maneuverable as when he ran. After all he could step off space or air.
He could also use his abilities to move the air and space around himself while functioning at superspeed to keep from doing things like turning the air to superheated plasma.
Kai could also do the same to objects. Though he couldn't wrap big things up as evidenced by what was left of the I-beam he tried moving. The heavy bag was still doable though.
He also figured out that he was pretty much stuck at perceiving everything many times faster than normal though if he concentrated he could slow it down to 10 times faster..
He had a sort of 360 degree 'sight' like the kid on this one anime about ninjas his grandma made him watch, only he didn't have a blind spot.
Kai could also pass through things. Testing this was also how he discovered three other things.
The first was that if he wasn't careful when phasing through something, then said thing would blow up. This also led to the second which was that he healed very very fast and could even grow back limbs. Well, a finger at least.
The third was that he could live for an indeterminate amount of time off of the energy he absorbed. As far as he could determine regular breathing, sleeping, and eating were pretty much optional.
On the final day as he packed up the items he brought with him. Kai noticed his grandmother landing outside of the complex.
—--------------------------
0.000001 nanoseconds later
Mai landed on the road leading into the complex.
She then took two steps. At this point she tried to leap back as Kai seemed to materialize in front of her. However she couldn't budge even an inch.
She noticed that Kai was holding her wrist and calmed down slightly.
"Sání… We need to talk…"
"Kai!? How did you… Where… "
She looked around and then back at grandson.. "Let's go inside and talk."
"Ok..."
Mai's vision blurred for a moment as she felt something touch her legs and upper back. Before she could react she was standing in the gym within the complex with Kai standing in front of her.
She immediately threw up.
'Oh… Right. Conservation of motion…'
"Sorry grandma."
Mai looked back up at him as she wiped her mouth with her sleeve.
"It's OK. At least you figured it out by doing it to me. If I had been an A rank you would have just liquified my internal organs. Just keep that in mind if you're going to carry people."
Kai's eyes went wide with horror.
'I need to be more careful…'
"Yes ma'am!"
"Good, just keep it in mind. Now, you said that we needed to talk? I'm assuming part of that entails how you moved that fast just now…"
"OK. I'll start from the beginning."
Over the next couple of hours Kai explained what had happened and the hypotheses he had come up with about his powers.
Once he was done explaining she sat there for a full minute before speaking.
"Well someone has been keeping up with his studies… Listen Kai… We never had this conversation and if anyone asks, you only control lightning and wind."
"Can I tell John?"
"No. This has to be our secret. John's a good kid but if anyone finds out about this there could be big trouble."
"Won't people notice something though?"
"Well fortunately you're already registered as having S+ rank potential. You're also the only S+ rank that can control both lightning and wind so you're bound to develop some unique abilities."
"..."
"It should be fine as long as… Just don't move at full speed around S ranks or higher and you should be fine. Also the government and the Academy won't be letting the public know about your actual rank until after you've graduated anyways."
Kai's brow furrowed. "Why would they do that?"
"So foreign governments and criminals don't target you. To everyone else you're just an S rank. At least until you graduate. So you're going to have to stay low-key"
"So… passing through stuff is ok?"
"HELL NO!!!"
Mai rubbed the bridge of her nose then looked at Kai. "Just try not to do anything you can't explain away with S rank lightning and wind control. Low-key is the name of the game."
"Grandma."
"Yes Kai?"
"Is everything this slow for you too?"
"You get used to it."
"Oh good, talking like this is hard."
"Well, we've still got 5 years before you officially start Hero training. It should be plenty of time. We can at least get you fully acclimated to your powers by then so you can interact with people and not accidently hurt anyone."
"Great… Ummmm… Sání."
"Yes Kai?"
"Can I still run instead of flying?"
"But flying so much fas… Oh, right… You said you figured out how to run on air… It's fine if you want to run."
"YES!!! Sání so I can be like the comic hero?"
"Wait what comic hero?"
Kai dug into his backpack and showed her one the comics. It had a man covered in lightning wearing a red and gold outfit with a lightning bolt going through a circle on his chest.
Mai stared at the comic in his hand for a moment. "HAHAHAHA!!!" Yes shíyázhí you can be like the comic hero. If I remember right you might be able to do some stuff like his nemesis."
"... But, you said not to go that fast."
"Oh… Right… Yeah nevermind, bad idea."