“Uni Spoon” from new Izakaya in my neighborhood. What is the pink under the caviar?

So the menu just says "uni spoon" with no further description. Obviously we have uni, then I'm fairly certain the other items are quail yolk, salmon roe, sturgeon caviar, and something pink under the caviar. It was very mild compared to the other flavors. Is it some type tuna? It wasnt quite a paste, but it was very finely minced. Not as dark and milder flavored tha maguro. Might not have been fish at all.