(Ash's POV)
'As I understand it, in short: you are afraid Ash would be unhappy that you really want to become Yuki's Pokemon. Mostly because of everything he has done for you. You feel as if leaving him would be considered a form of betrayal.' I hear Tapu Koko ask Greninja, confirming the basics of his long explanation.
'...Yeah.' Was the response my ninja frog gave.
For the past thirty minutes, I've been hiding on the outside of the Ruins of Conflict, listening to their conversation. I know it's rude to ease drop, but he was acting so... off earlier, that I was extremely concerned. I now understand why.
He wants to officially be Yuki's Pokemon, but he also doesn't want me to feel like he wasn't thankful for all I've done for him. This surprised me... the fact that he didn't say a word to me. Doesn't he know that I respect his wishes? If he really wants to be Yuki's official Pokemon, and of course she's willing to accept him, I would be more then happy to make that happen!
I was snapped out of my thoughts when I noticed Tapu Koko was very close to the entrance. 'In the words of Ash Satoshi Ketchum from this morning: I may of caught Greninja, but Greninja is his own Pokemon. I'm sure those words also apply to this wish of yours, right Ash?'
I felt his hand grab my own arm and pull me into the Ruins of Conflict, where Greninja was sitting... exactly where I found Yuki on her first day.
"Uh... hey, Greninja. Sorry for ease dropping..." I felt embarrassed and somewhat upset with myself, but not as much. Despite me feeling bad about listening in, I was too worried about my friend!
'Don't worry about it, Ash.' Greninja smiled back, then gave me a nervous expression. 'So... now you know... how I fe-'
I didn't even let him finish. I ran upto him and gave him a reasurring hug. "You should know by now that I respect the wishes of all my Pokemon! Just because we had that special bond and it's suddenly gone doesn't mean the way I treat you will change. If you want to become her Pokemon, then I'll help make your wish come true!"
I backed out of the embrace and gave him what people tend to call my signature smile. "Let's go back to the house and talk to Yuki about this. I'm sure she would be glad to have you as her very first official partner."
I could see a smile radiate from Greninja's face, one that made me feel good... it was a smile that expressed that I was making the right choice.
_____
When we walked back inside, Yuki seemed to of woken up at some point, as she was at the dining table, eating. (Seemed to be steak, which looked soooooooooo good!) Pikachu, who was on the floor, seems to have stolen the Ketchup Bottle from the table...
It only took a moment for Yuki to turn her head towards the door and... see Greninja's change for the first time. To our surprise, it was extremely well received! As I sat down and had some steak, she explained to us what her dream starter would of been if she came into this world under different circumstances.
"You see, even before I knew about Greninja's special form with Ash, I easily grew fond of Greninja's in general. When I played the games that represented Kalos for the first time, I chose Froakie as my starter. I beat the game with that Pokemon, fully evolved. Over the course of the next couple years, I learned of what it's Shiny form looked like. Let me tell you: It's no exasperation that I instantly fell in love with the Pokemon even more." She then shoved another piece of steak in her mouth before continuing. "I thought to myself that if I was ever magically isekaied into this world, I would easily want my starter would be a Shiny Froakie or just a Shiny of that evolution line. If you're sudden color change is from what I think it is, then it makes a lot of sense to me why it turned out this way..."
No one has told Yuki how things turned out like they did yet, but leave it to a 24-year-old in a 10-year-old's body to easily catch onto something like this.
As dinner just finished, Greninja walked up to Yuki. He looked at me, looking to see if I was still OK with his decision. Of course I was! I gave him a nod, which his attention went back to his hopefully soon-to-be new trainer.
'Yuki, I have a request.' The ninja frog looked down at his webbed feet for a moment, composing his facial expression. I could tell he was so nervous...
"What's up, Greninja?"
Picking up his face, he asked the question. 'Yuki, will you catch me?'