in mIRC, type /font and then choose the one you want (you may have to test a few to get what you want). If you type it in a channel window, or query window then you can also check the set as default box for that type of window.
click on view-->options >irc-->messages and see if you have the sjis/jis conversion box checked or not. (you can also click on tools--> options to get there)
