Make Sae like this at any time

Ren had to admit, this was hotter than he anticipated. So he had a fun idea in mind.

"Sae," Ren whispered into her ear as he kept fucking her. "Whenever I say 'Key Ignition', you'll return to this car state. However, when I twist your nipple, it'll turn you on as a car, and you'll be idle, simply making low engine noises...until I fuck you just as I am doing now. Once my dick enters your pussy, it'll be the equivalent of shifting gears to drive, and you'll go into full car mode. Louder engine noises, faster bouncing, the works. Got it?"

"VRRRM VRRRRM VRRRRRRRM!" Sae said. Ren took that as a yes.

As for Ann, Futaba, and Makoto, he still had individual triggers to test...and he wasn't done with his Sae car yet. He could sue a 'show for the road', as it were.