Cheese toast is the open-faced answer to the cheese sandwich: one thick slice of bread, cheese laid across it, the whole thing run under heat until the top blisters and the edges go lacy and brown. In a Japanese kissaten it tends to arrive as a generous slab of shokupan, toasted so the underside stays firm while the cheese bubbles on top, warm enough that the first bite stretches. It is breakfast, a snack with coffee, a small warm thing eaten standing up. The pleasure is direct: crisp bottom, soft middle, a savory molten lid.
The technique is all about the gradient through the slice. The bread should be cut thick enough to hold structure under the cheese, toasted so the base crisps without drying to a cracker, while the heat from above takes the cheese past melt into faint browning. The cheese is usually a melting type, sometimes a processed slice for reliability, sometimes a shred that browns into a deeper, nuttier flavor. A good one has three clear zones: crunch at the bottom, tender crumb in the middle, and a glossy, just-scorched cap of cheese on top. A sloppy one is either pale and rubbery because it never got hot enough, or scorched bitter at the edges while the bread underneath went tough and dry all the way through.
From this base the slice takes additions easily. A crack of black pepper, a drift of sugar for a sweet-savory turn, nori or shirasu in the local idiom, a fried egg dropped on top to push it toward a full plate, honey trailed over a sharper cheese. Once you build it up with ham and a second slice and turn it into a closed grilled or pressed sandwich, you are somewhere else entirely, and that somewhere deserves its own article rather than being crowded in here.