This fun and slightly whimsical scenario offers a lot of opportunity for exploration. It starts with the idea (a fad, I'm told, in some places) of combining sushi with nudity, and branches off from there into territory ripe with potential for sensation play. Along the way, it introduces a novel twist on the good old-fashioned nipple clamp.
Sushi for Two
In some places, there is a tradition involving eating sushi rolls off the body of a naked person. The practice is called "nyotaimori" or "nyataimori" (in Kanji, , from woman, body, and arrangement), and it allegedly has an accompanying ritual that goes along with it. There's some question about whether or not this is really an art form in Japan or just a fad that appeals to prurient Westerners, but regardless, it's fun, especially when you dispense with the tradition and add a few twists of your own.
Bring chopsticks, though. We'll use them later. In fact, you'll probably want at least two pair handy, even if you'll be the only one eating the sushi.
Of course, you can't have naked sushi without sushi and a naked person:
The arrangement of the sushi on the naked person is pretty straightforward. You might want to keep the wasabi and soy sauce in a separate container, though. The sushi itself is part of the sensation play, as it's often served cold, and many people find the feeling of cold objects on their skin erotic.
Since half the point of sushi is in the display and arrangement, you can arrange the sushi on your partner's body in any way you find aesthetically pleasing.
Traditionally, the rules of nyotaimori forbid addressing or touching the person upon whose body the sushi is served. Since we're doing this for fun, that rule goes right out the window. Feel free to stroke and caress your partner during the dinner; in fact, you can run the ends of the chopsticks lightly over sensitive parts of your partner's body, or if you like warm sake, even rest the sake glass lightly on your partner's skin. Optionally, you may even blindfold your partner before you begin, to intensify the sensation.
Eating the sushi is only half the fun. As you proceed, you can integrate more and more sensation into the experience, touching your partner lightly or running your chopsticks over your partner's body. Once you're done with the sushi, then you can really start playing.
Take a small rubber band and loop it over a pair of chopsticks near one end, to hold them together moderately tightly. Then take another small rubber band and loop it more loosely over the other end of the chopsticks. You can then use the chopsticks as a kind of nipple clamp, by spreading them apart and placing them over your partner's nipple:
The tightness is easily controlled in two ways: first, by how many turns of rubber band you wrap around the chopsticks at the far end, and second, by how far you move the rubber band down the chopsticks (moving the rubber band closer to the end increases pressure; moving the rubber band closer to the center of the chopsticks decreases pressure).
You can experiment with a variety of other forms of stimulation as well. One good toy in keeping with the overall theme is bamboo skewers, which are thin bamboo rods pointed at one end. These can be dragged slowly over the skin, or pressed into the top of a clamped nipple. The neck, behind the ears, the sides, and over and around the breasts are good places to run the skewers.
Hot and cold are also logical choices; keep some ice cubes and some hot sake handy (the small ceramic sake cups transfer warmth well).
What you'll need
Sushi (whatever variety you prefer), a couple of sets of chopsticks, some small rubber bands, and a small dish for your wasabi and soy sauce are a good place to start. Those are only the beginning, though. You can integrate all kinds of sensation play into the experience, so you may want to keep some of the various tools and toys talked about in the sensation play sections on hand.
Bamboo skewers are cheap and easy to find at any grocery store, and fit the flavor and theme of the sushi meal nicely.