Someone ther eahs to have 3 hands. You see the girl on the bottom's right arm bending upwards before it's cut out of view and her left hand is plainly visible.
The girl on top's right hand is plainly visible by "bottom's" left hand. That leaves 2 hands on crotches. Unless they have hands growing above their crotches.
I don't see how could Kaede could have 3 hands. I mean, the hand that's fingering her is obviously Sara's, and Kaede's hand is in turn fingering Sara. Not that hard to see.