The chicken katsu sando is the lighter sibling in the katsu sando family: a breaded, deep-fried chicken cutlet on soft shokupan, painted with thick tonkatsu sauce, crusts usually trimmed and the sandwich cut to show a clean cross-section. Against the pork original it reads as the leaner option, more neutral in flavor, leaning on the panko crust and the fruity-savory sauce to carry it. It is a known quantity in convenience cases and katsu shops alike, the sandwich you pick when you want the crunch and the sauce without the depth of pork fat behind it.
The whole thing turns on the cutlet and the contrast around it. Chicken is pounded to an even thickness, dredged, coated in coarse panko, and fried so the crust goes deep gold and shatters while the meat stays moist rather than dry and stringy. The shokupan should be fresh and pillowy, often spread thin with butter or mustard to seal it against the sauce, with the tonkatsu sauce applied generously enough to season every bite but not so freely that the crust turns to mush before it reaches you. A good one keeps an audible crackle against soft bread, the sauce sweet and tangy and assertive, the meat juicy edge to edge. A sloppy one is a dry plank in a damp coating, under-sauced so it tastes mostly of bread, or fried so long ago the panko has gone soft and oily. Sometimes a layer of shredded cabbage adds a cool crunch and a little relief from the richness.
The variations split mostly on the cut of bird and what dresses it. Breast gives a leaner, more uniform bite; thigh runs juicier and more deeply flavored; the choice changes the whole sandwich enough that each deserves its own article rather than being crowded in here.