Here is the fight,

Between a 15 year old destroyer of world, 

And an old man.

"So," he said, as leisurely like he was talking to a baby, "I shall start."

"Ara? Won't you let the lady have the first punch?"

"Oh, missy. You aren't a lady, no. You are a disgusting disease."

Kun?! That was damage. Okay, witty answer, witty answer. Think of one.

"I, If I am a disease, then you are communism"

Okay, that was bad.

That was soooo bad.

Oh my god, I wanna die now.

That was so embarrassing!

I wanted to say that communism failed to remove diseases, but, but.

I wanna cry.

The man however, didn't seem to cringe at my comment at all.

He just looked up, at the ceiling.

"You had such a bright future."

That...awakened something in me.

Don't say things like that, please.

"You ruined your future you know, just because of your stupidity."

I was. I wasn't stupid.

"Do you even feel remorse for what you did?"

"I am evil. I do bad things."

"You aren't a child. Excuses won't take you anywhere"

Stop talking to me!

"Fight, you coward!"

Despite my outburst, the man just seemed to be more disappointed.

"I gain nothing from this. I am just...just. I want you to live a happy life. This path you are walking on, it is simply a dream."

Shut up, please, I can't hear anymore.

"I know exactly what you are thinking, you defeated the demon lord, so you let it get to your head. You got arrogant. Shelfish. Overconfidence leads to failure. 

Are you even listening to me?"

"No."

"You know what we call those who don't listen even after being told many times?"

"No."

"Idiots."

"I am not..an idiot." I spoke for some reason. I didn't wanted to speak, yet my mouth was ruining everything.

"Hoh? How are you not an idiot? Just for...no reason. For no reason at all. You destroyed your life, and that of countless others, for no reason at all."

"I...am not."

"I heard you wanted friends, but now you are lonely. No one shall even remember you ever lived. No, they would be glad you died."

"Mastwer, is that man troubling you?"

He is saying mean things about me.

"He is lying then."

I don't know

"He ish! Mastwer knows bwest!"

I don't.

"Does mastwer know what she wants to do?"

To make others happy

"Thwat makes mastwer best!"

Wand...I love you.

"Hehe. I wuv matwer too."

But you might be wrong

"Nwo! Mastwer is best!"

"I am really?"

"Un."

"Hey, old man. Shut yer trap, and COME AT ME!"

"You....as you wish."

He simply flexed his arms, and many layers of circles appeared, as if he was wearing bracelets.

Pointing at me, he turned his hand and the circles glowed at changed.

Instantly, from the ground, many chains appeared, and even before I could blink, I was binded in them.

They were magical, of course. And completely restrained my movements.

Ara, this is troublesome, I can't spin my wand.

I really wanted to spin it, but doesn't seem like there is any choice.

Wand chan, increase my strength please

"un."

I tried to move around my shoulders and just broke the chains. They just shatter. 

But the man wasn't shocked at all, he just repeated what he did, and I was chained again.

Grr, let me spin my wand.

I jump this time before breaking them, high, as high as ceiling, which was very high by the way. As high as a church. I was practically flying.

Again he raised his hands, but this time there was a faint blue cube around me. Same blue that was the shield around the city.

Foolish.

Let my wand spin!

"Mastwer wheeeeeeeeeeeeeee"

A pink beam just passed through the barrier, aimed straight for his knee. But he dodged to the right, just took a step.

I take a deep breath.

"Listen, I don't wish to kill you.

And you can't kill me.

Surrender, or else..."

"Or else what?"

"Or else I'll surrender."

"Wh-what?"

"I have no intention of fighting someone weak. You are free to attack me as much you want, I won't dodge. Pinky promise."

"Are you mocking me?"

"Yes. Yes, I am. You are weaker than me, and I am having pity on you."

"Hoh, provoking me won't work, littl-"

"Shut up and fight, you loser."

"Hmmm. I see, so you are not interested in chit chat. 

Unfortunately for you, I am here to experiment.

For generations, my family has been trying to develop sealing magic.

And you are gonna be the lab rat for them aAAAAAAAAA...YYOOOUU..FU..AAAGHHHH."

Hehe,

I waited just for the right moment to shoot him. He was too boring after all.

Now then, what persona I should choose?

The "I don't remember giving you permission to speak" type

Or

"Haha, can't believe you fell for it. What a fool" type.

Wand?

"Maswer, how about mixing both?"

I don't remember giving you fell for it. What a fool?

">.< no. Tell him, Don't you remember what I said? What a fool."

Ala, such a naughty wand.

"I don't remember you...wait. You..are stupid."

That was so bad!

">.>;;"

"Yo..you...arghhh."

Eiiii, too much noise, its hurting my ears.

Wand, heal him.

"~^^) un."

And just like that, the wound was healed, tho much blood was lost. The carpet had a big red spot. The walls were ruined. Oh my,

I really need a maid here.

And I am bored.

"Heyyyyy, oji san, could you just do your stuff an-"

This time, he was the one who didn't let me complete the sentence

 A force pulled me down, crashing into ground, creating a dust cloud.

I couldn't even get up before I felt something tickling, something climbing up on my body.

A tree root, slowly, no, quite fastly climbing, wrapping me around.

It grew thicker and thicker, and almost like a coffin, wrapped me up.

"This spell," said the man, "is an improved version of what was used to seal the First Demon lord.

A perfect fusion of elements.

Very inefficient, consumes lots of mana,

But it looks cool,

A fitting seal for you."

I didn't answer, I was too curious what was happening around me. 

The tree had covered me, smells really fresh. Like moss. 

Soon the tree became moist, I could feel my clothes sticking to my body. Everything was becoming cooler.

"Masta! Something bad is about to happen! Should I harden your body more?"

Yes.

Soon, I hear crackling.

The water droplets began to fizzle.

Small bubbles were being released with a fizz.

Electricity, huh.

What's next, fire?

Yes, it is fire. Everything was becoming warmer and warmer, but not much.

Say, wand. How much hot is it?

"x.x) very hwot. Enough to roast you"

"Roast me to a kebab?"

"Roast wou to awshwes."

Ala, that's very hot.

But, it is time to end this facade.

There is not enough space to spin my wand, so that is very sad.

May the trees themselves degrade,

A simple spell,

To end all,

Increase randomness,

Increase devastation

Let the disaster commence.

The tree rot, I was free, and bored.

Spin spin spin, 

Let this man,

See a nightmare.

The man had his eyes widened, and took a few steps back. His face was half opened and his legs began trembling.

I am not interested in him however, I just laid on my bed. He can do whatever he wants now,

Good night people