What happened with Japanese WMMA? 6 years ago there were a lot of japanese ladies in international ratings, but now i can remember only Hamasaki between top-fighters
I would say a combination of factors.
-a lot of the scene's Japanese "stars" retired.Miku, Tsuji, Shinashi, Watanabe, all retired around the same time. Shinashi and Watanabe have returned, but fighting infrequently and not against top competition.
-The death of Smackgirl. When Smackgirl folded, you had the fighters split between Valkyrie and Jewels, with a smattering in other promotions like Deep. Some say competitive organizations is good, but not when it's such a small niche that divides people's attention. Valkyrie didn't last long.
-The rise of the women's scene in the West, namely North America. When WMMA was on the fringe of the sport in the U.S, many American and other western fighters went to Japan to fight, because they knew fights were available there. Now, it's the opposite. WMMA is the hottest growing thing in the sport in North America. There are women in the UFC, and a women only promotion with Invicta. The focus has shifted, and there's less incentive to travel outside the States.
-Except for a sparse few, the Japanese fighters, both male and female, seem either content to stay on their islands, or just aren't as willing to leave their comfort zone.