The Japanese club sando is the western club sandwich passed through a hotel-cafe and kissaten sensibility, which mostly means restraint. The familiar cast is there, ham, a layer of egg, lettuce, tomato, sometimes a swipe of mayonnaise, stacked between toasted shokupan and pinned with picks. What is different is the scale. Where an American club tends to tower, double-decked and bristling with bacon, the Japanese reading is lower, tidier, and more composed: a sandwich you can pick up and bite cleanly rather than a structure you have to negotiate. It is comfort food plated with a cafe's eye for the cross-section.
The execution is about balance and a clean cut. The bread is soft milk-loaf shokupan, lightly toasted so it holds the fillings without shattering or going soggy under the tomato. The egg is the layer that most distinguishes the local version, usually a folded omelette-style sheet or a thick mash of egg salad rather than a few thin slices, which gives the sandwich a soft, custardy spine. Lettuce is shredded or layered crisp for a cold snap; tomato is thin and patted dry so it does not flood the bread; the ham is mild and folded for height without bulk. A good one has each layer distinct, the bread structural, the egg generous, and a tight diagonal cut held by picks so the strata stand up on the plate. A sloppy one is over-tall and unstable, the tomato weeping into pale untoasted bread, the egg thin and the whole thing sliding apart on the first bite.
The variations track what a given cafe keeps behind the counter. Some add a layer of chicken or turkey to nod harder at the American template; some run the egg as a fried egg with a soft yolk instead of a folded sheet; some skip tomato in winter and lean on cucumber for the cold crunch. Hotel coffee shops often plate it with a small salad and crisps and cut it into four picked triangles, which is closer to the genre's home register than the deli counter is. The towering bacon-heavy American club it descends from is a different animal in proportion and intent, and that one deserves its own article rather than being crowded in here.