Tatsuya Madoka is a friend of mine as JIDOHOSHU on 2ch@IRC . He has meetings on #日本大好き (“We like Japan” in iso-2022-jp encoding, of the Japanese standard for IRC). He advertises that channel everywhere. So he could collect many members. I have a channel: #政治討論 (Political Debates) but few visit and we seldom have meetings there. He operates his channel for how to have Japan attracted among young Japanese people.
* In Japan, 2ch@IRC is the most famous since 2ch is the biggest Japanese forum site. Another most famous is IRCnet since you cannot find few documents about other IRC networks. I always recommend xchat2 since you can recognize that there are many IRC networks in the world. xchat2 is a UNIX client but you can get also the Windows version.