3 months solo trip in Asia this autumn

Hello, I'm planning a 3 months trip from end of september to end December in South East asia.

So far I'm planning :

5 weeks in Japan, starting in hokkaido, then going South by train to Tokyo, Golden route and then down to Okinawa

3 weeks in Taiwan, seems amazing

5 days in Hong Kong

And then I'm not sure... Indonesia or the Philippines? It will be December than, I'm not sure about the weather, I' d like to end the trip somewhere quiet on the beach ...

What would you recommend ?