Some shops do nothing but wagyu sandwiches, and that single-mindedness is the whole story of the wagyu sando specialty. Rather than a fixed recipe, this is a context: counters and small specialist operations organized entirely around marbled Japanese beef between bread, where the menu is a set of variations on one luxury idea rather than a sandwich list with a beef option buried in it. Walk into one and the choices fan out by preparation, a seared steak version, a thin-sliced rare version, a lightly battered cutlet version, sometimes a sukiyaki-style simmered version, each on soft crustless shokupan and each priced according to the grade of beef inside.
What distinguishes the specialist format is control over the variables that decide whether expensive beef survives a sandwich. The bread is chosen to disappear: fine-crumbed shokupan, lightly dressed, never assertive enough to argue with the meat. The beef is cut and cooked to spec for each style, the steak rested so it does not bleed into the crumb, the rare version sliced thin enough to stay tender, the cutlet fried briefly so the breadcrumb stays a thin shell rather than a thick jacket. A good specialist build shows the work in the cross-section, marbling visible, doneness deliberate, the bread dry at the seam. A weak one leans on the wagyu name to excuse a careless build, overcooked grey meat or a sandwich so fat-slicked it falls apart, charging a premium the execution does not earn. The format's promise is precisely that the kitchen has thought about each preparation rather than treating beef as a single trick.
Because this is a category rather than a single sandwich, the variations are the menu itself, and several of them stand on their own elsewhere in the catalog. The premium seared-steak version and the regional named-herd versions in particular each carry distinct logic, and the steak sando deserves its own article rather than being crowded in here.