A guy from social media who usually goes by 0317Akira and oxakiraox is rumored to be Kamen Rider Grease's actor. As far as back in July, he showed excitement over Kamen Rider Build's press release and even playfully questioned who might be in the show. In one photo, he even referenced Kamen Rider Grease's color scheme, gold, silver and grey.
俺の実験とお前の実験
さて、どちらが上かは戦えば分かるさ…
My experiment or your experiment?
Well, the superior one is determined in battle…
[Source: Build Rider News]