Cover bamboo sushi mat with plastic wrap. Lay a 1/2 nori sheet, shiny side down on the sushi mat.
Wet your fingers with Tezu and spread 1/2 cup sushi rice evenly onto nori sheet.
Line the edge of the nori sheet at the bottom of the bamboo mat.
Place the sweet potato at the bottom of the nori sheet, then add the avocado.
Grab the bottom edge of the mat while keeping the filling in place with your fingers and roll it into a tight cylinder, tucking the fillings in firmly. Lift the edge of the mat slightly and roll forward will keeping gentle pressure on the mat.
Wrap the rolls in plastic wrap to keep them from drying out while you make the other rolls.
With a sharp knife, cut each roll into 8 pieces. Keep a single layer of plastic wrap over the rolls while you cut to get a cleaner slice. Also clean your knife after every couple of cuts.
Serve with a side of edamame.
Sushi is best eaten the same day as the rice gets hard in the refrigerator. If they must be kept in the refrigerator, keep covered in plastic wrap and then wrap in a kitchen towel.