Si , Shi , 'O_o
Hi

sometimes when a Japanese write a japanese word in romaji , writes si instead of shi

for example : Kakashi ~ Kakasi

??

is it only certain girls ( mostly who uses atashi more than whatashi )

or is there another explanation

ありがとうございます。

Question

Si , Shi , 'O_o
Hi

sometimes when a Japanese write a japanese word in romaji , writes si instead of shi

for example : Kakashi ~> Kakasi

??

is it only certain girls ( mostly who uses atashi more than whatashi )

or is there another explanation

ありがとうございます。

Answer

Kakashi is written by Hepburn system of romaji, Kakasi is written by Nihon-shiki or Kunrei-shiki system.
Your can read more about it in Wikipedia.

Answer

Hello, GTO.  こんにちは

We often use more  "shi"  instead of  "si".

"shi" is hebon-shiki.

At school, we learn Hebon-shiki Romaji so 
"shi" is more commonly used.

In a passport,  names are also written in Hebon shiki too.

http://en.wikipedia.org/wiki/Romanization_of_Japanese