The shrimp rice burger is the one variant that forks at the filling itself: it shows up either with tempura-fried shrimp or with grilled shrimp, and the two are different enough in the mouth that it is worth deciding which one you are getting before you commit. Both keep the shared rice-disc frame, two pieces of seasoned short-grain rice pressed and griddled until the outer grains crisp; what changes is whether the seafood inside crackles or whether it comes off the heat tender and clean.
The frame is the constant, and its craft is the same everywhere in the category: rice compressed warm, griddled so a firm thin crust sets while the interior stays soft and grainy, holding as one piece to the last bite. The shrimp is the differentiator and the variable that decides the whole thing. In the tempura reading, the pleasure is contrast, a brittle fried shell against soft rice, and the failure is batter that has gone soggy from sitting, or shrimp small enough that the breading dominates and you are mostly eating fried crust on starch. In the grilled reading, the shrimp is sweeter and springier and the disc stays cleaner, but the risk shifts to shrimp overcooked into rubber, or so lightly dressed it reads bland against the mild rice. A good one, either way, has shrimp you can identify as shrimp by bite rather than by sauce alone, a light dressing or mayo binding it without flooding the disc, and something fresh and crisp tucked in for a third texture.
When it lands, the appeal is the layered crunch a meat filling cannot give you in the same way: rice crust, then the brittle or springy seafood, then the soft grain underneath. It eats lighter than the beef variants but the tempura version in particular can sit heavier than expected, since fried batter on pressed rice is more substantial than its size implies.
It belongs to a family sorted entirely by what goes between the discs. The yakiniku version is the rich, sauced-beef end; the chicken version stays lean; the kinpira version goes vegetarian with burdock and carrot. Each of those is a clearly different eating experience that deserves its own article rather than being crowded in here.