This is based on j-pop singers under the Hello! Project name.
From left to right:
Miuna Saitou (from Country Musume)
Airi Suzuki (from Aa!/ C-ute)
Ai Takahashi from (from Morning Musume)
Yurina Kumai (from Berryz Koubou)
Yui Okada (from Viyuuden)
It's so hard to draw proportions, I really need to work on that.