When someone is talking about Shinobi Ren, it's usually in a hushed whisper, as if the mysterious criminal figure could hear them if they spoke too loudly. The information is usually speculative rumor and wild tales. Few have ever met this Shinobi Ren.
Regardless, he is one of the top criminal figures on Yara Von, and he operates out of the Yorktown casino Oceans Front. He has encountered the players shortly after their escape, and was thinking about offering them a job, until he saw details on the ship that Rolph intends to use.
Something about his mannerisms and even appearance seem "off". It's like meeting a Californian who behaves like a mix between surfer and samurai. Even the appearance doesn't match the name, you would have expected someone of ancient eastern descent, not the slick dressed figure from a clearly more western descent.
Regardless, Shinobi treated you with respect, offered you amazingly expensive drinks and services. The encounter ended with his annoyance however, as you were unable to reach a deal for a job.