Takaaki-san,
I often mistakingly type CJK letters in TextMate documents by totally forgetting checking what input method I'm in.
If this happens, I don't find any solution to go back to normal. Pressing Command-Z doesn't seem to help there. The only thing I can do is close the window without saving, which, invariably, loses what I've been working so far.
Is there any solution to quickly revert to where I was?
The only way I know is to switch easily your Input Menu back to 'British' or whatever (apple-space switches to the last input method). Then TM will display what you entered. So you don't loose any data.
Cheers,
Hans