Preheat the oven to 400 degrees.
Mix the rice vinegar, salt, and granulated sugar in a bowl.
Using a saucepan, warm the mixture on low heat until the sugar dissolves.
Once it has cooled, pour the vinegar mixture over the cooked rice. Make sure that it’s evenly distributed.
In a different bowl, mix the mayonnaise, sriracha, imitation crab, and cream cheese until smooth.
Then, add the diced mango and cucumber pieces.
Layer your casserole by placing the sushi rice on the bottom.
Spread the creamy mixture on top of the rice.
Top with the furikake.
Bake for between 15-20 minutes.