User blog comment:Ghmorello/Chapter 905: What A Load Of Green Bull!/@comment-24850639-20180525181341/@comment-24850639-20180529150119

Norman - The popular speculation about Ryokugyuu is that his actor may be Yoshia Harada. He appeared in a movie called "Rouningai" with the actors that Fujitora (Shintaro Katsu) and Kizaru (Kunie Tanaka) are based on.

Here's a picture from his youth that people  think Oda will base his appearance on:

https://www.discogs.com/artist/4250677-Yoshio-Harada