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
Can the room change use without rushing the bedding away?
If a guest room in your Bucharest flat becomes an office each morning, walk through that change before choosing a shikibuton. Can you raise the bedding without moving the desk, and leave it airing before storage? Measure the sleeping surface, cupboard access and the selected model's folded dimensions. Folding is useful when the whole sequence works, including the period between getting up and putting dry bedding away.
HIMARI is 210 cm long with approximately 10 cm total thickness; SORA is 200 cm long and approximately 12 cm thick. Compare HIMARI's firmer feel with SORA's fuller cushioning as well as their footprints. Someone accustomed to deep softness may need more discussion before choosing either. Check the selected variant's weight and agree who will handle the morning lifting and airing.
How do I choose between HIMARI 日葵 and SORA 宙? · How do Japanese shikibuton sizes compare with local bed sizes?