What's amazing about hentai-kana (hentai as "alternative form", not pervert) is that governments and town registrars still allow using them as an official name in their electronic registry. I recently got a copy of my family register, and found out that my grandma's name was officially in hentai kana. Apparently they made special fonts for each unique character, but I don't know how they're encoded on their database. It was kinda awe-inspiring how much they care the details like that. They could replace it with a regular kana but they didn't. Names are serious business!
住民基本台帳収録変体仮名 (jūmin kihon daichō shūroku hentaigana, or Jūki-gana for short) is the character set specifically made for the administrative purposes of those local government registrars. I don't know what the actual computer system used there is based on, but it looks like Tron Code and Super Kanji support the character set.
https://commons.wikimedia.org/wiki/Juki-Gana
The thing about hentaigana is that it's more or less an open set. I don't think there is the standard set of hentaigana that scholars agree upon. At a quick glance, juki-gana does not seem to be identical to Unicode's hentaigana set (https://www.unicode.org/charts/PDF/U1B000.pdf), although I'm sure the intersection is non-empty.
I used ヲ instead of ウォ in my name in my hanko. It’s katakana, not hentaigana but you don’t see it except in old documents when they used to use katakana for particles (it’s equivalent to を). Saving the extra character meant I could get it made in ten minutes instead of one day. It sometimes gets comments when I use it.
By the way, there’s no requirement that your hanko matches your name and they only need to be registered for large purchases, like a house or for business use. They are however kept on record by your bank and sometimes compared digitally. By law foreigners can always use a signature instead of hanko but it’s not recommended as the comparison will often fail. On the other hand, online banking ans ATMs are good enough now that it’s been a good five years since I set foot in a bank.
> By the way, there’s no requirement that your hanko matches your name and they only need to be registered for large purchases, like a house or for business use.
There is a requirement for it to match your name (or registered alias) if you want to register it as a 実印, no?
When they say "only need to be registered for large purchases, like a house", they're talking about a 実印 - a 銀行印 is not "registered" in that sense (it will be on file at the bank, of course).
