Natsuki's papa (なつきのパパ Natsuki no Papa) is a character from Initial D, He is an unseen character, later revealed to be father of Shiraishi and Miki. 'Papa' drives a Mercedes E-class (in the manga, Papa drives a W201 Mercedes Benz 190E).
He was a salaryman who paid Natsuki to go out with him. In the manga it is specified that they had a sexual relationship. It was unclear if they had a sexual relationship in the anime.