Disclaimer: In my country, a “middle name” usually refers to the mother’s maiden name.
Sharing this in case it helps someone:
Wife gave birth last week and went to city hall today to report my baby. I learned that if your child has a middle name and you don’t yet have proof from your embassy (birth report/passport can take over a month), city hall may register the name in the Japanese order: Middle name + Last name, then Given name(s).
As a result, my baby’s 住民票 and residence card shows her name starting with my wife’s maiden/middle name, while my wife, son, and I all show my last name.
What surprised me is that my son’s birth was processed at a different city hall with no issue—they didn’t “separate” the middle name and just treated it as part of the given name. This city hall refused to do the same and insisted on declaring the middle name.
Their suggestion: keep the Japanese order for now, then once we get her passport, go back to city hall to correct the name order, and then request the update with immigration.
Honestly, it’s such a pain having to do all these extra changes.
by Low-Chard6435