Yes, a shikibuton can develop mould if moisture stays trapped underneath it, and that is true of any bedding on a floor. To reduce the risk with HIMARI or SORA: lift it off the sleeping surface each morning, check the underside and the base for dampness, let both dry, and air the shikibuton regularly in dry weather.
Why moisture collects underneath
During the night the body gives off warmth and moisture. Where the shikibuton meets a cooler, less ventilated surface, that moisture can linger, especially on non-breathable floors, in humid seasons, or when the shikibuton is left down for days at a time.
Habits that keep it dry
- Fold it into thirds or stand it up each morning so the underside can breathe.
- Air both sides regularly in dry weather, turning it over and rotating it head to foot.
- On wood, laminate or other non-breathable floors, use a moisture-absorbing pad underneath and dry the pad itself regularly.
- Keep a removable sheet or cover on it and wash that cover often.
- In humid rooms, run a dehumidifier or air conditioning, and do not store the folded shikibuton against a cold, damp outside wall.
If you notice spots or a musty smell
Dry the shikibuton thoroughly in a well-ventilated place, check the floor or base beneath it, and improve the airflow before using it again. Do not soak or machine-wash the whole shikibuton; for substantial marks, consult a cleaner experienced with futon bedding.
HIMARI and SORA
HIMARI 日葵 and SORA 宙 both have a 100% cotton cover and fold into thirds, which makes daily airing straightforward. SORA’s 50% premium wool blend is breathable, but no filling makes a shikibuton mould-proof: the routine above matters more than the material.