Just returned yesterday on Silver Whisper from Sidney to Tokyo (34 nights) and then around Japan (another 9 nights). It was a fantastic cruise! I had read some lacklustre reviews, but found them to be inaccurate moaning. Excellent entertainment and staff, food very good, lectures hit or miss. After 78 years on earth, this travel experience rates in the top 3!
We had to get e-tourist visas for Australia, but all other visas taken care of by Silversea and billed to account while on board.
Japan required all food to be served by staff (no self-serve in Panorama Lounge or at buffets). Also required were daily temperature checks usually performed by suite staff in the morning. They caught us on the way to breakfast (or if I was up too early, I stopped by reception).
If anyne wants more specific information about ports of call or tours, let me know. I could only read posts once I returned to the UK, so sorry this wasn't more timely.