Okay... First off:
Way too short. A fanfic chapter should be one page of text AT LEAST. Second: Not enough description. What's the shrine look like? The Alakazam? The ice? Everything should be described in detail. Here's some quoting...
Pokemon Island was a place of fun in the sun. Until now...
That's not really good enough. You should tell more about the island in a starting paragraph. Show the readers with words what the island is like, who its inhabitants are, and over all
why it's a place of "fun in the sun".
A Alakazam jumps toward the figure.
An Alakazam. Any noun that starts with a vowel (other than long U) must have the word "an" rather than the word "a" in order to refer to it.
They attempted to run to the hotel, but ice collumns raised out of the floor, blocking them.
What hotel? You never said anything before about a hotel. Before you mention "the" thing, you must mention "a" thing. So, if this is the first mention of this hotel, you should call it "a nearby hotel", or something like that.
Then, a whole bunch of rocks freeze, slowly coming together....
In any work of writing, unless it's from a certain person's perspective and you're really aiming for the voice of that person to be known, descriptions like "a whole bunch" are a bit off. You could use "several rocks" or "many rocks", and it would sound a bit better.
Pikachu will be in the next chapter.
Not really part of the story to critique, but considering the audience doesn't yet know who Pikachu is, telling us this isn't that important. Even if this is a Pikachu we should know (like Ash's Pikachu), we'll figure that out on our own.
One more thing: you seem to shift between past and present tense often. By this I mean, one sentence you'll be saying something "happened", as in it previously occured, and the next something "happens" as in it is occuring right now. Past-tense is normally good for keeping the same tense in a whole fic, and present-tense is normally good for oneshots, or specific sections of fics if used properly, but it's generally good to keep the same tense throughout your fic, especially if there's no flashbacks or special bits added in at the time.