Sunray Zoanthid (Palythoa sp.)
This could be a Sunray Zoanthid (Palythoa heliodiscus) or a (Palythoa lesueuri) タマイワスナギンチャク. They both look the same to me. Whichever it is, it is best to leave it alone because zoanthids are known to be very toxic. Amami 2026