Start by mixing the rice vinegar, sugar, and salt in a small bowl until dissolved.

Place the rice and water in a small pot without a lid over medium-high heat. Once it begins to bubble along the edges, cover with a lid and lower the heat to low. Cook for 13 minutes or until the water is absorbed.

Remove the pot from the heat and let it sit for 10 minutes with the lid on.

Remove the lid. Pour the sushi seasoning over the cooked rice and gently mix until combined.

Press the seasoned rice into a flat, even layer in an 8x8 inch baking dish. Press down as firmly as possible (can use another baking dish to press down). Refrigerate overnight or minimum 6 hours to firm up. 

Once the rice is set, cut the chilled rice into 15 rectangles or 20 small bite-sized squares using a sharp knife. Heat oil in a large skillet over medium heat and fry the rice pieces until golden and crispy on all sides, about 2-3 minutes per side. Place them on a paper towel to drain off any excess oil.

In a small bowl mix together the raw tuna, sriracha, kewpie mayo, sesame oil, green onion, and salt. Top the crispy rice cakes with thinly sliced avocado slices, your sushi-grade tuna mixture, a jalapeño slice, and a sprinkle of sesame seeds. 

Arrange the crispy rice sushi on a plate and serve immediately. It's best enjoyed fresh while the rice is still crispy.