Place the sushi rice in a strainer and rinse under cold water until the water runs clear. Place in a sauce pan with water and bring to a gentle boil over high heat. Stir, cover the pan, and reduce heat to low. Simmer for 16-18 minutes or until all the water has been absorbed and the rice is tender. Remove from heat and let sit with the lid on for 10-15 minutes. Scrape into a bowl, top with ¼ cup seasoned rice vinegar, and gently mix with a fork.
Combine the tamari with 1 tablespoon rice vinegar.
Combine the mayonnaise and sriracha. Put in a squeeze bottle or a sandwich bag (snip off one tip before drizzling).
Divide the rice between four bowls. In sections, place the imitation crab, cucumber, avocado slices, carrots, and cilantro. Combine the sesame seeds and sprinkle over the top. Crumble the nori sheets and place in the bowl. Top everything with sesame seeds and drizzle the spicy mayonnaise over the top. Add some pickled ginger and drizzle with some tamari sauce. Serve the remaining tamari sauce on the side.