We were originally a sub-forum (one among several, but the largest one) at JPopMusic.com. That site died, however, so the admin moved us all to a new, hosted forum…http://jpopcentral.yuku.com
Things did not go well there. The forum itself was slow and difficult to use, and the admin was hostile towards us. He didn't like having his forum so closely associated with idol music, because he pretty much thought all idol music was trash, and he'd hoped that we would get lost in the move.
So we looked for somewhere else to go. Zunu and boinsie had already set up this site as an unofficial backup to JPM, for some place to hang out when JPM was down (as it often was towards the end). We simply made it official.