Kimonos is the Swan and Dolphin has been most people's sushi go-to for years on property, but they aren't an "on property" restaurant...no DDP.
We've gotten sushi at Tokyo Dining a few times, it's in line with the average sushi place you may have in your hometown. Teppan Edo offers a little sushi selection.
Polynesian has the Kona Island Sushi Bar, I haven't eaten there but it looks like th selection has increased. Morimotos and Splitsville are great, but are sushi (rolls) and not nigiri or sashimi, IIRC.
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