How should I choose sizes for guest rooms, children’s rooms, or two people?

For one person daily, 100 cm is a good baseline; choose 120 cm if you are larger or move a lot; the 140 cm Extra-Wide Single is spacious for one and can suit two smaller sleepers, or lay two shikibuton side by side. For children's rooms, the low height, easy storage, and side-by-side option are advantages — pair with a protector, clean regularly, and manage base moisture.

Use this answer as a buying guide before choosing between HIMARI and SORA: compare feel, thickness, storage, available size, and whether you want everyday Japanese bedding or a fuller flagship shikibuton.