Its a shame cause Tarnyan is probably my favorite queens blade character as far as design goes. I wish she was more popular. As for Sainyan my theory is that Hobby Japan said it was a trap just so they could show fully exposed nipples in their book and get away with it lol. Im guessing if rebellion gets a full anime season then they will finally give us a definite answer on his/her gender.
Sainyan is now said to be ambiguous in gender, like said above they just got away with the full nipple exposure. :D However seeing the latest development on the QBR products and story we can say she's officially another flat chest loli. Though true they might change that again in the upcoming anime.