I really want to like rice burgers, but I've had a few now and every time they lose structural integrity before the burger is finished. The nori wrap might be a savior for that a bit, spreading the pressure from the hold, as well as removing any moisture from fingers. The lettuce on the inside will help as a barrier on one side internally too.

I'm yet to get over to star since I've been in Sydney, so I should at some point, and Gojima is certainly on my list of places (as is Sokyo, but money...)