>>5520606damnit forgot pic
And why the onahole you ask? She only has two biological bits, skin and vagina, we have to keep things simple. And yes, I find the idea that she literally 'thinks with her vagina' when it comes to regulating biological functions incredibly funny.
P.S. I just realized that making use of that onahole's 'horny hormone' as a vasodilator for her skin means she will get sopping wet down there during combat or overexertion. Kinky.
P.P.S. Forgot to mention that it can't be just a vasodilator, it should be used to trigger sweating too in higher concentrations. And delightfully, this also reproduces humans blushing, sweating hard, and getting really wet inside when fucking. Huzzah, I just managed to rationalize being both a horny fuck and a pragmatic engineer.