It is an interesting start to have the protagonist's father get arrested all of a sudden like that, and with a lot of mystery to it you certainly leave me wanting to know why. =p I would argue that it would have had more of an impact if you had not mentioned that part in the opening sentence though, so it would also come as a surprise to us the readers.
Overall though the beginning is interesting. Note though there are some common errors that could be improved upon. Let's start with the beginning:
I watched as they shoved my Dad into a police car, my Mum had tears streaming down her face, along with her I to was crying, but I had my Shimama to comfort me. The day started of ordinarily enough, I had came home from school to my Mum who was making dinner, whilst my Dad would be at work, he worked for one of the most successful companies in the region, what region you ask? The Unova region.
Firstly, off over of there - but the main thing of note are the run-on sentences. You typically continue a sentence on with a comma well after it should have all rights ended. For instance the second sentence there tells us that the day started off normally, then that she came home and what her mother was doing, and then what the dad was doing, what his work was and then tells us a direct-question in a 4th-wall-breaking manner, which is too much information crammed in. Rather, something like this:
The day started off ordinarily enough. I had came home from school and greeted my Mum who was making dinner, whilst my Dad was at work. He worked for one of the most successful companies in the region of Unova.
This way the pacing is set right and it dos not sound as rushed. On previous mention, I would advise from having the narrator directly address the readers with a question like this (i.e. breaking the 4th wall - talking to the audience from within the story) as it merely distracts from the tale itself.
“Mum, how come Dad always has to work late?” A medium height teenage girl, with Blonde hair and deep Blue eyes asked her working mother.
Another thing to watch out for is Randomly capitalising things that Shouldn't be capitalised. =p Colours are not proper nouns, so they do not need a capital. (One can argue the same for Mum and Dad earlier As for A - the part following the dialogue flows on from it and thus can be treated as one sentence together with it (but it would not sound right if it was its own sentence separate from the dialogue), and so there is no need to use a capital A there as the sentence does not start there. So for instance:
“Well Rachel, he's trying to close a deal, if he does, we can finally take a real trip to Sinnoh, Kanto or maybe Hoenn!” Her Mum answered.
works better as:
“Well Rachel, he's trying to close a deal, if he does, we can finally take a real trip to Sinnoh, Kanto or maybe Hoenn!” her Mum answered.
because 'her mum answered' does not work as its own sentence and refers to the dialogue (by telling us who said it).
Also note the change in perspective - you begun from the POV (point of view) of Rachel (I watched, my dad) to a 3rd person one (a girl, her mum, she...). It reads a bit oddly and probably can be done without as the transition is a bit clunky.
She looked down to see a small Zebra like Pokemon,
Zebra-like.
“Aww, hey Shimama,” Rachel smiled as she lent down to pet the Pokemon.
Note that punctuation of some sort is always needed in dialogue too, such as the comma I put in - as the part following the text flows from the dialogue and hence a comma is there.
Shimama let out a cry and darted upstairs, throwing Rachel onto her bed and started to nuzzle her, he didn't act like a Zebra, more like a common Growlithe, they played together for a while until a car door slamming snapped them out of it.
Note the run-on sentence problem again - you continue it too long by changing subjects too often there. You talk about what it does, then how he doesn't act like this but acts like that instead, and then that they did this until that happened - try breaking each part into separate sentences with each subject change.
“Come out” Rachel softly laughed, the red and white ball opened up and shot out a white burst of energy, revealing a small green Pokemon, it had short stumpy arms and legs, but a cool attitude, it had a short tail; the end of it looking like a leaf.
Along with the previous remark, try also expanding upon descriptions. It's a good start to already mention what things look like, but showing us rather than telling is a more engaging method. Take 'but a cool attitude' for instance - it tells us about its personality/attitude, but suppose you instead showed us what suggested to Rachel that it had a cool attitude? Say the way it looked at Rachal and folded its arms for instance - if you mention that instead, it's more interesting to read that 'but a cool attitude' as something is happening (no matter how small the action), but still
shows us h has a cool attitude without telling us directly.
That'll do for now I suppose - just a few things I though I'd mention. Oh, and... *shakes fist at Hiiro and Sydian* =p