Cross from Tokyo into the Kansai region and the tamago sando changes shape entirely. The mashed egg salad gives way to a thick slab of dashimaki tamago, a rolled omelette built from layers of beaten egg cooked with dashi, slid between two slices of soft shokupan. Bite into a Kansai one and you get a single warm-or-cool plank of egg with a faint savory broth note running through it, bouncy and slightly springy under the tooth rather than creamy. It is the same name as the Kanto sandwich and a completely different object, and that split is the central axis the whole tamago sando family turns on.
The craft lives in the omelette, not in any dressing. Dashimaki comes together by pouring thin layers of seasoned, dashi-loosened egg into a rectangular pan and rolling each set sheet onto the last, building a dense banded log that is then cut to the width of the bread. The dashi is the signature: it carries kelp-and-bonito savor and a touch of sweetness into the egg, so the filling tastes seasoned from within rather than from mayonnaise on the outside. Many shops do add a thin smear of kewpie on the bread, but it is support, not the binder; the omelette holds itself together. A good Kansai sando has a dashimaki that is thick enough to dominate the sandwich, tender and just-set with no dry overcooked edge, the layers visible as a fine spiral when you look at the cut face, and enough moisture that it stays juicy without weeping broth into the shokupan. The failures are an omelette overcooked to a tight rubbery brick, dashi so heavy it leaks and turns the bread to pulp, layers rolled loose so the slab falls apart in the hand, or a slice cut too thin so it reads as a token of egg instead of the main event. The bind problem here is the inverse of the mashed style: the omelette must sit flush and stay structurally whole between the slices, juicy but contained.
This is the omelette pole, and its closest sibling is the Kyoto style, which pushes the same dashimaki idea toward an extra-thick, soufflé-fluffy slab from a handful of well-known shops. Reaching back across the divide, the Kanto style keeps the finely mashed homogeneous salad, the double-egg build tries to bridge both worlds in one sandwich, the half-boiled version runs on a jammy soft yolk, and the demi-glace treatment adds a dark Western sauce. Each of those is a distinct technique with its own logic and deserves its own article rather than being crowded in here.