To clarify what Thomas said, some dive sites like Osezaki permit diving in buddy pairs or buddy teams, but none allow solo diving. If you show up alone and say that you want to dive solo, they will make you dive with one of their guides.
At almost all sites, you sign a waiver stating that you will adhere to the buddy system, going through the checks, evaluating the dive site conditions, planning the dive, etc. and you will be a safe diver, adhering to the accepted safety practices.
At almost all sites, you sign a waiver stating that you will adhere to the buddy system, going through the checks, evaluating the dive site conditions, planning the dive, etc. and you will be a safe diver, adhering to the accepted safety practices.