These futa girls are anatomicly inacurate in that they have a penis AND clitoris. The clitoris and the penis are both of the same type of organ, made of the same tissue. Having both of them is like having two hearts or two stomaches. Anyone who doesn't believe me, do some research on human anatomy, and you'll find that if you trace back the eariest developement of the clit and the penis to the fetus stage, you'll find out that they orginate from the same organ.
An acurate futanari should have a vagina and a penis with no clitoris and no testicles.
But, this is the Internet, and a futanari with an assumably 'usable' vagina and penis ought to be an anatomical impossibility anyway. Next time you have a stiffy, press between your scrote and anus, and tell me how far anything could go down a penis-imbued vagina.
