Take eight kanikama sticks and cut them into small pieces (about three millimeters) and put the pieces into a small bowl. Kanikama comes in the shape of sticks, but you can pull them apart into smaller strips. When you mix in the Kewpie, you need to mix a bit aggressively to break up the pieces of kanikama.
Cut the avocado in half and remove the pit. Take a spoon to remove the halves from the peel. Cut the avocado into thin slices. Julienne the cucumbers into thin slices.
Cut the nori sheet into half sizes along the shorter end of the sheet (like hamburger style if you remember from elementary school). Take ¼ cup of rice, and using your hands, layer the rice evenly on the sheet. Dip your hands in the water bowl to keep your hands from sticking to the rice.
Sprinkle sesame seeds over the rice.
Turn the seaweed and rice sheet over and add the kanikama and Kewpie mixture along the middle of the seaweed. I like to add about three tablespoons of kanikama to end up with a roll that is one and a half diameter in size.
Layer the avocado slices and cucumbers horizontally along the kanikama mixture.
Take the bottom edge of the sushi mat and slowly move the nori sheet over the filling, completely wrapping the spicy tuna and rice in the sheet. Use an upwards motions with the sushi mat to guide your spicy tuna roll upwards. Keep the roll tight by applying even and gentle pressure while rolling upwards. Be gentle to prevent your nori from breaking or having rice or fish from coming out the sides. Continue this motion until your roll comes away from the mat.
If you are having a hard time tightening your roll, wrap a sheet of cling wrap around your sushi roll and tighten by using both index fingers and thumbs to pinch the sides of the cling wrap while simultaneously rolling your California roll forward. This should look like a candy wrapper.
To cut your roll, take a very sharp knife and cut in long, one stroke slices. You don’t want to run your knife back and forth because this could tear or damage the roll. Wipe your knife after every cut to prevent rice from sticking.
Serve your California roll with soy sauce, wasabi, and gari.