Mix 1 tbsp rice vinegar, 1 tsp sugar and ½ tsp salt together in a bowl until dissolved.
Pour the mixture over 320 g cooked Japanese short-grain rice while still warm. Mix gently yet thoroughly using a rice paddle while fanning to cool, then cover with a clean damp tea towel to prevent it from drying out.
Optional: Turn your gas burner on low and carefully fan 2 sheets roasted seaweed for sushi (nori) over the fire to improve the texture and aroma.
Fold the nori in half, pinch along the crease and then neatly tear down the fold. (Use scissors if preferred.)
Place your bamboo rolling mat on a flat surface in front of you with the bamboo laying horizontally. With the rough side facing up, align the long side of the nori with the bottom of the mat.
Wet your hands and take a handful of sushi rice (approx 80g / ½ US cup). Shape it into a rough cylinder.
Spread the rice out to the edges leaving a border along the top, pinching along the top edge of the rice to make a ridge. Thoroughly mix 2 packs natto until foamy, then spread the natto through the middle, using half a packet per roll.
Lift the bottom of the mat and roll until the edges of the rice meet.
Press firmly, then lift the edge of the mat and roll once more to seal.
Wipe a sharp knife with a damp cloth and cut the sushi roll in half.
Cut each half into thirds, wiping the knife between each cut.
Enjoy with a small bowl of Japanese soy sauce (koikuchi shoyu) for dipping!