[XeTeX] question about japanese tex file

[Akihiro Moriguchi]

Hello.

My name is Akihiro from Japan.
I just installed and stadying how xetex treats japanese(utf-8) under 
CentOS 5.

Just I compiled tex file including japanese text in utf-8 with xetex 
command, but couln't get
Japanese output in which english are correctly displayed.
Any preindication (command) needed when there's japanese in source file?

I got log output below.
Each words after "There is no " are a Japanese character.

This is XeTeX, Version 3.141592-2.2-0.997 (Web2C 7.5.6) (format=xetex 
2007.10.14
)  15 OCT 2007 00:34
entering extended mode
**test.tex
(./test.tex
Missing character: There is no は in font cmr10!
Missing character: There is no て in font cmr10!
Missing character: There is no な in font cmr10!
Missing character: There is no な in font cmr10!
Missing character: There is no に in font cmr10!

I'm quite new to tex system as just starting "TEXbook" by Knuth.
Please direct me to good reference, manual or tutorial.

Thanks in advance.
Regards,

Akihiro Moriguchi