Tanuki is the name of spezific japanese forums. Everyone on there is anonymous and they talk about almost every band. Topics can be the newest single or which member they like the most ect. But tanuki is more famous for spreading rumours, either good or bad ones. Like, how they slept with bandmember XY, what their real names and ages are and such things.
Sometimes these girls (I suppose that most of the people are girls) spread awful things about bands. REALLY awful things which are hopefully lies. >_ <
But as I said, infos from tanuki are not realiable, though funny and interesting at times.