Scrub the sweet potatoes well. Grate the sweet potatoes on the small holes of a grater, then grind it in a mortar into a paste.
Transfer the sweet potato paste into a bowl and mix in the flour and salt until it’s well combined.
Cut your nori sheets. Spread the sweet potato mixture about ¼ inch thick on the pieces of nori to make the kabayaki.
Heat about ¼ inch of oil in a pan. When the oil reaches 325°F, gently place a few pieces of kabayaki nori-side down in the oil.
Once they’re browned, remove them to a wire rack over some paper towels to drain.
In a small pan, whisk together the soy sauce and sugar until combined. Set the pan over medium heat and bring it to a simmer.
Heat a grill pan or other grill. Brush the sweet potato side of the kabayaki with the glaze, then set them on the hot grill.
Lay the pieces of kabayaki onto some brown rice, brush with a final layer of glaze, and serve.
