The first part of the tuna to explore is Ootoro. This is the most desirable part from the inside of the fish’s belly. Because it is the fattiest part of the fish, it practically melts in your mouth with a rich fat taste. Because of its rich and highly sought-after nature, the Ootoro can be a bit more expensive than other parts of the fish – but certainly worth every penny. As tuna fat melts at a lower temperature than human body temperature, it dissolves quickly in your mouth, and we love to enjoy that sensation.