@toonsense
Will owning a residence in Japan automatically make me a tax resident of Japan?
Not necessarily. Tax residency is based on the entire facts and circumstances of your life. You also have to take into account the effect of tax treaties (which give you the right to avoid being treated as a tax resident of both countries simultaneously, at least with respect to income tax).
Normally, owning a "vacation home" does not make someone a tax resident of Japan, because a vacation home is not typically the "base of a person's life", as required by Article 22 of the Civil Code. But if you were to move most of your belongings to the property, for example, and spent more time there than at any other residential property, then it could start to be seen as the base of your life.
there is some sentence about “maintaining a domicile continuously for 1 year or more"
Be very, very wary about English translations of the laws around this topic. There are a lot of misleading translations out there. I strongly recommend the
tax residency section of the wiki, which walks through the relevant statutory provisions in detail.
The sentence you are quoting is not an accurate reflection of the law. As explained in the wiki, the one-year rule is a failsafe that applies to people who live in Japan but
do not have a "jūsho" in Japan. (Jūsho is often translated as "domicile", but that can be misleading.) Owning a property in Japan is not "living in Japan" in the context of the one-year rule. It requires actual physical presence in Japan.