Pour rice into a large bowl and rinse in cold water. Drain and repeat 3-5 times. Transfer the rice to a pot and add the water. Mix, bring to a boil, cover, and then turn the heat down to a simmer for 15 minutes. Switch off the heat then allow the pot to rest for 10 minutes. Don't remove the lid during the cooking or waiting. While the rice is cooking, add the rice vinegar, sugar and salt to a bowl and mix until sugar dissolves. Loosen cooked rice with a rice spatula or wooden spoon. Place rice in a large, wide, shallow, non-reactive dish. Pour vinegar mixture evenly over rice and mix using a spatula in a cutting and folding motion. The vinegar seasoning must be mixed while rice is hot. Allow sushi rice to cool to room temperature. Finely chop tuna and mix with sriracha mayonnaise, and chopped chives. Place a seaweed sheet on your sushi roller. Using wet hands, scoop out rice and place evenly over surface of seaweed sheet. Place three spoonfuls of the spicy tuna in a line one third of the way up from the bottom of the sheet. Roll and shape into a triangle.