Well, it looked like that you took some time on this story. You have a plot, you have some description. Hey, I'm just happy that you included Pikachu!
Your grammar is kind of shoddy. You're missing the punctuation in your dialogue before the closing quotation marks.
“About a minute” he replied.
See? Like here, you're missing the comma after "minute". There were many instances of this in your story. Just take a look through your story again and you should be able to find them.
Also, you seem to have a little problem between "its" and "it's". "Its" is the possessive form to show that something owns something. "It's" is the contraction of "it is".
As for description, I would ask for a little more, especially about how the characters feel in the situation, and a bit more about the surroundings and battle. But really, you did rather well, and put more into this than other "first time" fics I've seen.
Oh, and welcome to PC!