For the rice

• 1 Cup Uncooked If you can't get  Koshihikari short grain rice, you can use risotto rice or these Japanese rice substitutes. I like to cook my rice with 1 piece of 1-inch dried kelp, to give it extra flavor, but it's not really necessary! 
• ¼ Cup rice vinegar Substitute for the rice vinegar, sugar and salt: shop-bought sushi seasoning
• 1 Tablespoon white sugar
• 1 teaspoon salt

For the topping

• ¼-⅓ Cup Furikake Seasoning available at Trader Joes, Whole Foods, online, Asian markets and Japanese grocers. (You can make your own by mixing sesame seeds with small bits of seaweed and other ingredients.)
• ¾ Cup mayonnaise UseJapanese Kewpie mayo if you can. If you can't get it, mix ½ teaspoon of sugar with your mayo to give it more oomph. Sour cream should also work for this recipe but I've never personally tried it so can't advise on quantities yet.
• 3 Tablespoons cream cheese Take it out of the fridge 5-10 minutes before mixing with the mayo, so that it can soften. If not it's a pain to get a smooth spread.
• 2 Cans tuna 5 oz cans (but don't sweat it if the weight varied a bit.) In oil or water both work. This can be replaced with canned crab imitation crab meat or real crab meat 

Garnishes

• 1 avocado sliced, cold out of the fridge
• sesame oil Drizzle
• 1 prig green onions sliced thin
• 1 Tablespoon sesame seeds white, black or a mix, lightly toasted.

Optional, to wrap

• nori sheet Roasted, preferably, cut into palm-sized rectangles. Substitute: Korean gim seaweed