I haven't, actually! Thanks for asking! I'd say my first instinct is California, because A) a sizable amount of Japanese-Americans live in California, B) I feel that's a very easy place for NiceP to have scouted him after seeing him perform (show biz, baby). As a coastal enthusiast myself, C) since he's from Okinawa, I also felt like California's weather and climate might be more his speed (rather than, say, New York, where show biz would also be big)-- I could see him living along the west coast because he's tied with water and feeeeeesh. However, I also like the idea of him being from or going to Hawaii a lot. That state has both large Japanese AND Okinawan populations..

In the scene where he's hyping up Keito, he says "よっ、 あんたが大将!" with 大将 being "taishou" -- basically "Yo, you're the boss!", but I chose to make it "Yo! You're the big kahuna!" because of the reasons above, hehe.

TL;DR Ca. Li. For. Nia Boys. Are Unforgettable.