It's clear from the asker's wording and comments that what they are getting at with the question is, they want to know if there any mixed-transport route from Canada to Japan that's cheaper than simply flying; and they don't mind if this is a bit of an adventure, slow, unusual, etc; they'd just prefer for it to be less "prohibitively long" than going by sea. See for example:
when not restricting oneself to flights
I don't want to restrict answers to air travel only, all forms of transport should be considered if they can reduce the overall cost. Travelling to a neighboring country and taking a bus/ferry/train/etc. is a perfect example.
I don't think it's right to ignore an asker's clear, stated intentions in order to shoehorn a question into being a duplicate of a similar question. I've edited the title to make the difference a little more obvious, but this shouldn't be necessary, the asker made it perfectly clear already in the body of the question.
If someone here knows for a fact that nothing will be cheaper than flying a common route, great. That's the (disappointing, but probably true) answer to the question. Write it up as an answer, and state how you know. Don't hide your useful knowledge behind a close vote. For example, this comment:
Boats would never be cheaper than a plane for that distance
...is knowledge that, if true (and it almost certainly is), mostly answers the question. Share it, as an answer to the question, and state how you know.
As for the concern from one comment:
Otherwise we'd be spammed with an endless string of "Country A to Country B" questions.
This isn't just any old "Country A to Country B", it's an unusual question asking about possible off-the-beaten-track routes, including hitchhiking and ferries from neighbouring countries.
If Travel.SE was to one day become so successful that every adventurous traveller looking for off-the-beaten-track options for ambitious trips chooses this site to ask about them, great; that's not spam or a problem, we're not going to max out SE's servers, it's a sign of a flourishing travel site.