A shikibuton can retain moisture from the sleeper and the room. In humid conditions, lift it after sleeping, air both sides, keep the base dry and use ventilation or a dehumidifier when needed. A moisture-control pad can help, but it does not replace regular airing.
If you are comparing Japanese futon care with a conventional mattress, focus on airflow, dryness, regular turning, and the right cover; these habits help the shikibuton keep its shape and comfort.