I'll be There

Proper Use

Arriving at the intended address Midoriya couldn't help but think he showed up to the wrong place. The neighborhood itself wasn't the problem it was more of the fact that the house was run down and covered in graffiti. He just couldn't image a pro hero, let alone one that taught the number 1 living in a less-than-pleasant place like this.

He knocked on the door expecting to be told he had the wrong house; however, when he knocked on the door he realized the door wasn't even fully shut.
"Was this a break-in?"
The door didn't look tampered with and he didn't hear anything inside. That's when he decided to go in to see if things were okay. 3 steps into the house he saw a puddle of what seemed to be blood.

...

But when he leaned closer to examine it he caught a boot to the face so fast it sent him flying into the back of a couch.
"Gwaa!"
Looking up (not before checking his back for injuries) he saw a short old man in a funny-looking yellow costume.
'But those aren't normal boots, are they some kind of support item?'
"You gonna introduce yourself or keep gawking at me?"
Midoriya stood upright a little confused.
'If you wanted an introduction maybe don't start with a kick to the face'

"I'm Izuku Midoriya, hero name: Deku, All Might told me you used to be his teacher."

"Huh? Oh Toshinori, yeah I used to teach him back in the day. I'll tell you one thing I went too easy on the brat back then, that's why he thinks he can do anything now."

'He went easy on him? Just hearing his name made All Might hide inside of his office for half the day.'

"So how much of One For All can you wield?"

Suddenly the old man's 'old guy' persona disappeared, it was like a switch was flipped that gave him the aura of a relentless drill sergeant.

"You gone deaf or something kid? Or do you need another kick to jog your memory? How high can you go with One For All?"

"5 percent sir!"

"Only 5 percent?! What the hell has that idiot Toshi been teaching you?"

"He taught me-..."
Thinking back on it, while All Might did tell him the basics of what OFA was and what it was ultimately meant to be used against, he never really did teach him much on how to properly use it.
"Not much... really only just about the output..."

"..."

"..."

Midoriya could feel the temperature in the air rising with every second, it seems like the laid blackness of his teacher in actual teaching has pissed off a man that should never be too pissed.

...

Burning lungs and muscles, creaking joints, rapid breathing, and black spots in his vision, any sane person would've called it a day and ended the work out there, but the seriously pissed-off gramps had other plans.

"Alright kid boot up OFA and see how high you can take it"

Pushing himself up off the ground, Midoriya pulled together his fragmented mind and took a deep breath.
'3%.'
Things haven't changed much, there's a slight boost but not by much.
'5%.'
With this much, he felt confident that putting a hole in a wall would be like smashing a wet clay pot. And besides a little strain from his muscles, Midoriya felt he could keep going.
'8%.'
Now the drawbacks were apparent, it felt like there was a splitting pain in his skull, and he was worried that something like 15% would burst a vessel. The difference between 5% to 8% might not seem like much but the power was noticeable. The power in his legs let him know he could jump up a 3 story building. And just maybe he could take it up a notch.
'10%'
That was a mistake, instantly it felt like his blood was razor blades, or if a windy breeze hit his raw muscle tendons, he released OFA immediately and fell to his knees.