Posthumous divorce’s technical but less popular name is a “notification of marital relationship termination” (inzoku kankei shuryo todoke) which means one is officially severing ties with the family of a deceased spouse. What’s particularly strange about it is that it doesn’t really serve any purpose for a vast majority of people aside from a government-approved official statement that someone finds their in-laws unbearable.
Its dual, unless you are picking a fight with the Japanese government for citizenship.
As much as I want to fight them to the death over it, I fixed the spelling. My wife is still reluctant to get US citizenship, so I’m ready to duel on her behalf!