We had done the same thing with my father, and now I am doing the relay of the removal of my mother's name from the register with her death.
A journey through the life (and place) of a mother -- The bureaucratic cruise.
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I: "What am I doing this for?"
Sister: "It's to find our brothers and sisters we don't know."
In other words, if my father or mother has an "illegitimate child," that child will also have the right to be granted property.
If we don't "legally establish" that we don't have such a child, we won't be able to receive even the smallest amount of money in my mother's bank account!
Honestly -- it's a hassle, I think.
There are times when I think, 'I don't need that money.
However, if left unchecked, the remainder of the money will be collected by the treasury -- in other words, taken by the government.
It's perfectly fine if I don't get it, but it is absolutely unacceptable for the "state" to get it.
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In my case, just by thinking about it, driving all over Japan and going through the process of applying for a copy of the registry in a local area doesn't seem so "painful" to me.