1. Wash the rice well and drain (do it 5 times). Transfer the rice in the bowl and add enough water to soak. Soak for about 30 minutes.
2. In the meantime, make the vinegar seasoning. Add the vinegar, sugar and salt in a small cooking pot. And cook over medium heat until almost boiling. Melt completely the sugar and the salt. Set aside.
3. Drain the rice and transfer into a cooking pot. Add water (640ml). Cover and cook over medium-high heat, bring it to a boil. Once it boils, reduce the heat to low and simmer for 10 minutes.
4. Remove from the heat (do NOT open the lid yet!) and let the rice steam for another 10 minutes with the lid on.
5. Moisten a "Sushi-Oke" (or a large glass bowl), and transfer the rice into it. Pour the vinegar seasoning in one go. Slice the rice, let it cool down, using a hand fan occasionally.
6. Once it has cooled to room temperature, cover with saran wrap until you are ready to serve!