One thing to keep in mind if you visit a bathhouse is that unlike most onsens, you need to take your own towels and soaps. Outside the sento doors, we discovered an interesting charm stuck to the wall.
It reads:盗賊除神璽 touzokujyoshinji, burglar abolish imperial?/divine-seal (this bathhouse is under holy protection from thievery). That last character usually refers to an emporer's seal, but 神璽 can refer to either the emporer's seal or the Three Divine Regalia. Ultimately, it comes from 天(あま)つ璽(しるし) (The Mark of* Heaven), so I think this is actually referring to something like that in this case.
Also of note is that both 璽 and 盗 don't have the standard amount of strokes on this sign. Older/alternative forms, I'm guessing.
*つ is really old Japanese for の (of, the genitive particle).
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