A cream sando is the plainest possible sweet sandwich: lightly sweetened whipped cream pressed between two slices of crustless shokupan. There is no fruit, no jam, no custard layer, nothing to hide behind. That bareness is the entire point. It sits on the dessert end of the Japanese sandwich shelf, cold from a chilled case, eaten the way someone elsewhere might eat a slice of plain sponge with cream. The bread is soft and milky and barely sweet; the cream is cold, loose-bodied, and sweetened just past the threshold where you notice. Neither part is much alone. A slice of shokupan is breakfast and a bowl of whipped cream is an afterthought. Held together and chilled they become something with a clear shape and a clean, almost austere pleasure.
Everything depends on the cream and the chill. The bread should be a fine-crumbed shokupan, the milk-bread loaf with a tender, slightly chewy interior and the crusts trimmed flat so the slice is a clean rectangle. The cream is the variable bakeries fuss over: dairy fresh cream whipped to a soft peak that still flows a little, sweetened lightly, sometimes steadied with a whisper of mascarpone so it holds a flat face when cut rather than weeping into the crumb. The sandwich is built thick, the cream spread to the very edges so there are no dry corners, then pressed gently and rested cold so the layer firms before it is cut. A good one has a high cream-to-bread ratio, a level white band, and bread that stays soft because it was kept cold and wrapped. A sloppy one is thin in the middle and bald at the edges, the cream beaten so stiff it tastes of nothing but air, or so loose it has soaked the bottom slice into paste by the time it reaches you.
The variations are about what you do to the cream without breaking its plainness. Some shops fold in vanilla seeds for a fragrant version, or a spoon of mascarpone for a richer, almost cheesecake note. A milk-tea or hojicha cream gives a toasty edge that cuts the sugar; a faintly salted cream leans the whole thing savory. Push it any further and you have left the room. Add fruit and it is a fruit sando; add a cooked custard and it is a custard sando; arrange the filling for a photogenic cut and it becomes a cross-section piece. Each of those is its own creature and deserves its own article rather than being crowded in here.