First thing... the formatting on this was next to impossible to read in
Pine, and I'm sure that a lot of people had trouble reading it.

Cry me a river

Good title

The rain was beating a steady rhythm on the streets of night-time Tokyo. 
Mizuno Ami dodged through the rain, though her attempts at staying dry were
haphazard. 

haphazard isn't used correctly here

'shining aqua illusion.'.  She should be loving the sky's tears.  Yet she

I think it's "Shiny Aqua Illusion". Both these paragraphs set a nice mood
and are very well done.

 

The thing she ran from was herself.

This bit was good too.

A lock of unruly blue hair fell in her eyes, and she pushed it away,
juggling a shopping bag at the same time.   It had taken a fair amount of
convincing, but her friend, Kino Makoto, had finally convinced Ami to
accompany her on a shopping trip.  When Ami had finally grudgingly agreed,

you use shopping twice in a row. maybe a different word ?

I didn't think you'd mind."  Mrs. Mizuno stared coldly at her daughter.  

1. Ami really admires her mother. Ami works so hard because she wants to
be a doctor. It's also revealed later on that Ami's Dad is a real butthead
and Ami chose to live with her Mom, who she adored. Ami's parents are
divorced.

2. It should be Dr. Mizuno, not Mrs. Mizuno ^_^

"Do you have any idea what time it is?"  Ami nodded.

This is confusing because you can't tell who's talking.

"I know what those young people think .  I was once one, too, you know.".  

This COULD refer back to the prostitute line ^^; you might want to adjust
your phrasing.
 

love with it at first sight, and Makoto had finally convinced her to

purchise it.

purchase

Mrs. Mizuno looked at the skirt in her hands.  It was well-crafted, and she 
smiled cruelly as she gazed at it.

Ack. Ami's mom is really nice and caring in the manga and anime.

"How much did you spend on this skirt, Ami?".  Ami swallowed hard.  
"This week's allowance."  She whispered.

Uh. Ami's rich. She lives in a HUGE apartment in one of the nicest 
buildings in town. Not only is her Mom well off, but she gets money
from her Dad who is a famous artist (he belongs to an exclusive 
Health club and such)


"I didn't hear you, Ami.  Please repeat yourself more clearly.".  Ami
repeated 
herself, this time more loudly.

instead of "more loudly" maybe use "louder" because "more clearly" in addition
makes this part seem repetitive.

Ami raised her head.  Her eyes were pressed together in a evil glare, and her
breathing was shallow.

Ami wouldn't do this... I really don't see her acting like this. After she
slaps
Serena, she cries. Ami isn't violent. Even her attacks are usually not to
hurt,
but to protect.

"Okaa-san!  Nonononononononononoooooooo!!!!!!!!!"  Ami didn't know what 
to do.  A dead fear ran through her, and she bolted through the front door.
For reasons she didn't know, she grabbed her bookbag on the way out.

This part doesn't make much sense. How could she not know the reasons?

... Ami cried out as she tripped over a jutting rock.  Her feet deserted

her, 

and she fell, scraping her hands as she fell, landing in a mud-puddle.  The 
liquid was cool, and strangly refreshing.  She decided to stay there, just

for

a little while.

you use fell twice. try a different word the second time ^^


I think you show a lot of potential as a writer, but I do think this story
is strangely off kilter, at least in comparison to the anime and manga. Not
that this always matters, I have seen several fics that completely
disregard the author's original characterizations and do it well. However,
I think this fic, especially with Ami as the main character, seems
strangely wrong. Your imagaes at the begining are lucious and vivid, and I
think you could carry this through in a more meditative sort of story about
Ami. Keep up the hard work and you will succeed.

good luck,

misa