Hello Ryuhei:

I think it might answer a lot of your questions - and certainly give you a better understanding of what is involved in long-distance travel in far Eastern Russia - if you were to plan a little trip next summer (summer 2021) between Vladivostok and Khabarovsk, with the possibility of continuing further beyond Khabarovsk in the direction of Yakutsk if things are going well for you when you reach Khabarovsk.

I've visited both Vladivostok and Khabarovsk many times, although I always traveled between those cities flying an aircraft, not riding a motorcycle. I can tell you that the area within about 100 km of each of those cities is quite thoroughly populated, and the big gap in the middle between the two cities is mostly unpopulated. So, by making that trip (Vlad to Khab), you would get a very good sense of what motorcycle travel in rural Russia is like. You would also gain a good understanding of what possible logistical problems you might run into (language, motorcycle servicing, permits, etc.).

Vladivostok is not a very attractive city, and in my personal opinion, it does not offer very much to see. Khabarovsk, on the other hand, is a very beautiful city with remarkable late 19th / early 20th century architecture.

There is a saying "Learn to walk before you try to run." In other words, before attempting to do a round-the-world trip that begins by taking you all across Russia, go spend a couple of weeks exploring there, and see what it is like.

Vladivostok is quite close to Japan, and because of your knowledge of Japan and your ability to speak Japanese, you should be able to figure out a way to get you and your motorcycle to and from Vladivostok without much trouble.

Michael

PS: Apropos of your idea of travelling to Yakutsk on a motorcycle in the winter - FORGET IT! Yakutsk is the second coldest city in the entire fuggin' world (see the second paragraph of the Wikipedia entry about Yakutsk). I overnighted in Yakutsk once in January, and had to spend 2 hours pre-heating the aircraft engines from the outside before I could even attempt to start the aircraft engines - the overnight temperature had dropped to below -40°C.