Holy cow Byakuren is hot. Well-designed, sleek, and form-fitting, and the lotus in her hair is an excellent touch. Yuyuko is adorable too. The rest, no contest.
I always get a laugh out of whenever people look suprised that they're wearing a swimsuit. "Wha!? How!? I was wearing shorts and a shirt a second ago!" Normally I'd blame Yukari, Tewi, or Nue depending on context, but that doesn't work here.
Still tho, fantastic design choice. Indeed Hijiri and Yuyu's are both cute, sexy, fitting and creative.