Thanks for the good intel on SD.jp and SA.
I'm pretty much stuck stateside and haven't gotten back to Japan in a while (thanks COVID), and SA stateside has been okay for sugaring. I was seeing a 20 year old nerdy Chinese college student with a slender body (yum) and a liberal outlook on P4P, but she wasn't open to other requested services so things kind of petered out.
I set up an account on SD.jp a month or two ago just to see what it's all about, and I've been pleasantly surprised. All that I really put in my profile was basically "Hi, I'm an American and speak crappy Japanese, nice to meet you" (in Japanese of course), and I'd say most of the girls whose profiles I view also view my profile, and maybe half or a little under message me. Since I can't prove residency yet and I'm not in country I haven't bothered upping my membership, I haven't been able to see what they wrote much less write them back, but that's a much better response than I get on SA. I'm assuming that's because my usual preference is 'slender, very cute women' and Asian girls like that in the US are buried under messages from hundreds of guys interested in getting in their pants, where in Japan it's much more of a buyer's market.
I do wish they had much better searching functionality on SD.jp, but I'm definitely looking forward to getting back to Japan soon, and I know I need to improve my Japanese skill to have a proper conversation with these ladies.