In a saucepan over medium high heat; combine sugar, vinegar and salt.
Remove from heat; stirring until sugar and salt have dissolved completely.
Mix mixture into cooked rice.
Transfer rice into 9x13-inch glass baking dish.
In a mixing bowl; combine topping ingredients; adding mayonnaise as needed.
Sprinkle furikake over rice.
Spoon seafood mixture onto rice; gently spread out evenly.
Broil 5-7 minutes until browned and bubbly.
In a small mixing bowl; combine sriracha and mayonnaise.
Transfer into a squirt bottle (I re-use my sriracha bottles).