Stopped when he said he waited forever to get naturalized, skipping 6 years, and then saying he never got his permanent resident card, so he was just living off renewed visas, and they thought it was strange.
It is strange. A lot of the things he said he needed, would have been done in the permanent residence portion of his time in Japan. Just as it is in any country.
I thought Japan requires 10 years residence for PR, but only 5 years residence to naturalize, in which case it wouldn't be surprising if many people naturalize before getting PR!
Once you are living in the country for a while, you can pretty much do anything and people don’t care about your resident status at all. For my daily lives in UK I only need my address and driving license. You pretty much have the feeling that you’ll be fine without bothering to do the paperwork, that’s how things work in the last 20-50 years.