Rinse and drain the rice in cold water. Then place in saucepan with water, coconut milk and salt. Place the pot over high heat and bring the liquid to boil. Stir and reduce the heat to the lowest possible setting and cover the pot tightly with the lid and continue to cook for 15 minutes.
Remove the pot from the heat and let it stand for 10 minutes, covered. Fluff with fork and put in bowls.
Mix the soy sauce, lime/lemon zest and juice and ginger in a bowl and set aside.
Wash the tuna sashimi and cut into cubes, when it's ready place the tuna in the soy mixture and toss until it starts to change color. Make sure you don't toss it for more than 2 minutes.
To plate, place the rice in a bowl and drizzle a teaspoon of teriyaki sauce.
Drop the chunks of tuna on top of the rice and drizzle half a teaspoon of teriyaki sauce on top.