Ahoy Yzlian, If you hit bad weather (N winds) it can be nasty at the top due to wind<->current. Not our own experience but heard from others. Yes there is much traffic, but don't worry. They stick to shipping lanes. Fishing vessels are all well lit.
Akita? Don't know, or do you mean Hokkaido? Again, don't worry about the traffic.
Suppose you'll have AIS and RADAR.
Yes coming from HK and heading for Alaska, the west coast of Kyushu+Honshu is the way to go.
What boat are you sailing?
Sayonara, yap
Ahoy Yzlian,
April/MAy would be a much better timing to sail from HK to Japan.
I would take the East coast of Taiwan, as esp the N of Taiwan can be nasty. Mind you , you'll have to time to go around the S as well, but there are plenty of ports you can stop at. These days foreign yachts are welcome in Taiwan, see also our stories at HP. (mail me for the address).
Have a great trip.
yap