Yuu's actually still pure. The worst she could imagine is sleeping in the same bed.
And Touko also didn't reveal her true thirst yet. Maybe the readers are projecting just a little. Of course nobody knows what will happen once they are alone in an empty appartment. All alone~
Touko the schemer strikes again.
On the other hand, Koyomi has another chance to get closer to Renma-sensei. I think everyone predicted the way it would happen. Whether we get to see it though is a different matter. Maybe in a special.
Now excuse me as I rob my local pharmacist for copious amounts of insulin!