Choose HIMARI or SORA when the published dimensions fit your room and you can regularly lift, air and keep the bedding dry. Compare the firmer HIMARI with the fuller SORA by personal preference, storage space and the actual local offering. Thickness alone does not determine comfort.
Details to check before choosing
Measure the usable length and width of the floor, platform or bed base, including any raised edges. Compare those measurements with the exact model and size offered for your country. Then check the folded size and weight, and choose a sheet or cover that fits the same dimensions.
After sleep, lift or stand the shikibuton so you can inspect its underside and the supporting surface. Let both release moisture. Air both faces in a ventilated place, turn the bedding over and rotate it head to foot regularly. Fold and store it only when it is dry.
Sources for this answer
Would the morning routine work in my room?
If your Sofia bedroom also holds a desk, mark out the selected model with the chair pulled back and the door open. HIMARI is 210 cm long and approximately 10 cm thick overall; SORA is 200 cm long and approximately 12 cm thick. A shorter footprint may help the layout, but compare HIMARI's firmer feel with SORA's fuller cushioning before choosing by length alone.
Next, decide who will lift it after sleep and where it can air before dry storage. A cupboard reached only by shifting furniture may make folding a daily burden. Check the selected size's published weight and folded dimensions. If you want a high bed or deep sinking softness, describe that preference before committing. A workable layout and a suitable sleeping feel both matter.
How do I choose between HIMARI 日葵 and SORA 宙? · How do Japanese shikibuton sizes compare with local bed sizes?