Just a note that you could easily spend your entire 10 days in various parts of Japan and not scratch the surface of what the country has to offer.

Also do consider that travelling from Tokyo to the awesome dive spots in Malaysia (e.g. Sipadan, Layang Layang) or other South East Asian countries will easily eat up an entire day. For a 10 day holiday I'd not be so keen to spend 2 days travelling, but to each his own.