Steps

1. Rinse 220g of rice and soak in water for 20 minutes.
   🕒 00:00
2. Combine 100ml of soy sauce, 50ml of cooking sake, 50ml of mirin, 2 tbsp of sugar, and 8g of kombu in a pot. Mix well and let sit for 1 hour. This kombu soy sauce is the key to the marinated tuna; be sure to make it!
   🕒 00:21
3. In a heatproof container, combine 4 tbsp of rice vinegar, 1.5 tbsp of sugar, and 1 tsp of salt. Mix well and set aside.
   🕒 04:26
4. Place the soaked 220g of rice and 190g of water into a rice cooker and cook on the quick setting. It's crucial to use the quick setting because regular cooking allows too much time for the rice to absorb moisture, which can affect the outcome. Always use the quick mode.
   🕒 06:03
5. Remove the kombu from the marinade after it has steeped for 1 hour. Strain through a sieve and paper towel if necessary. The marinade will thicken, allowing it to coat the ingredients better and infuse flavor more effectively, even with a small amount.
   🕒 06:42
6. Gently pat the surface of the 180g of tuna scraps dry with paper towels and place them in a bowl. Removing moisture from the tuna prevents the marinade from becoming diluted and helps the flavor penetrate deeply.
   🕒 07:59
7. Add about 2 tbsp of the prepared marinade to the tuna and gently rub it into the pieces to coat evenly.
   🕒 08:45
8. Cover the bowl tightly with plastic wrap, ensuring the tuna is submerged in the marinade. Refrigerate for 10 minutes.
   🕒 08:57
9. Gently warm the prepared sushi vinegar in the microwave (600W) for about 30 seconds, then mix thoroughly. Avoid overheating, as this can diminish the acidity of the vinegar; lukewarm is ideal.
   🕒 09:17
10. Transfer the cooked rice to a large bowl. Pour half of the warmed sushi vinegar over the rice paddle and mix immediately into the rice.
    🕒 09:38
11. Add the remaining sushi vinegar and mix the rice by cutting and folding it with the rice paddle, being careful not to crush the grains. Repeat the flipping and mixing motion from bottom to top. Crushing the rice will make it sticky and prevent it from separating lightly in your mouth. Mixing while the rice is hot ensures each grain is coated evenly with sushi vinegar.
    🕒 10:16
12. Spread the seasoned sushi rice evenly in the bowl and quickly cool it down by fanning it with a fan. Leaving hot rice unattended will cause it to become sticky and lose its fluffy texture, and the acidity of the vinegar will evaporate, resulting in a dull flavor.
    🕒 10:52
13. Once the rice is no longer hot to the touch, cover it with a damp paper towel and let it sit for 5-10 minutes to allow the sushi vinegar to meld with the rice.
    🕒 11:31
14. Plate the sushi rice in a bowl, then top with the marinated tuna. Drizzle with extra marinade if desired.
    🕒 12:00