Note: I don't own Pokémon, I just own this story.
Goh came to Ash and said:
"Hey Ash, we are going to Kalos! The professor said there is areally strong Greninja!"
"Great! Let's go!"
They arrived in Kalos.
"The professor said that Greninja lives in this forest!" Said Goh.
Ash is thinking: "This forest looks kind familiar..."
They set their camp.
In that moment, Ash felt something. A familiar felling what is dragging him into the forest.
Ash stopped for a second.
"Are you okey Ash?"
"Yeah, just... I felt something... Like I felt that before and I must remember what it is... But I can't"
Goh looked worried.
"This feeling... Like it's dragging me into the forest... Can we go?"
"Of course!"
Note: For this part Pokémon will talk like humans, because they can understand each other.
In the meantime, on the other side of the forest, Greninja was walking with his friends Squishy and Z1.
Then, Greninja also felt something strange, like Ash.
"Are you okey Greninja?"
"Yeah, just... I felt something strange... I know I felt that before, but... I will just go into the forest."
Squishy and Z1 looked worried.
"Maybe we should follow him."
"Yeah."
Ash and Goh were walking through the forest. As they were walking deeper into the forest that feeling started getting bigger. In one point Ash saw Greninja and Greninja saw Ash. In that moment they both started running towards each other.
"Ash, where are you going?!"
They were running and running until they saw each other.
"Greninja?"
"Ja"
They were both in shock, but then they hugged each other so tight.
Then Goh appeared.
"Whaite a minute, it's that Greninja! You know him?!"
"Sorry because I must disappoint you Goh, but this is my Greninja."
"You have Greninja?!"
"Yeah."
Then Squishy and Z1 appeared.
"Ash, it's good to see you."
"Thanks, Squishy."
They went back to their camp. There, Ash explained everything to Goh.
"So, this is your Greninja, these two are Zygarde, you had to left Greninja to destroy roots, and you two can Mega evolve just with your bond?!"
"Yeah, that is it."
In that moment, Ash and Greninja felt something.
"Goh, watch out!"
Then GIANT root appeared.
"It's the last root!"
"Let's go Greninja, lets destroy that root!"
"Ninja!"
In that moment, Greninja became surrounded in a water veil and started transforming.
Goh was in shock and started taking pictures of the transformation.
"Go Greninja, use Aerial ace!"
Greninja started punching roots, but nothing happened.
"Now use Cut!"
But again, he didn't do any big damage.
"Then we will finish it with this, go Water shuriken!"
And they did it! They destroyed the roots!
"We did it!"
Greninja transformed back to its normal form.
"That was awesome!"
"Thanks Goh!"
"That was the last root, that means Greninja can now go with you Ash!"
"Really?!"
"Yeah."
He took Greninja's Pocke Ball.
"What do you say Greninja, will you travel with me again?"
"Ninja!"
They were both in tears.
"I am now in the Pokémon World Championship, and with you in my team I will definitely win!"
"Ja!"
That is it for this chapter. I will do my best and if I get enough support I will make more chapters.