My opinion is there is no regulation. But these are the best places to watch beautiful kimonos so you might be watched.
The homongi wearers you may see at the entrance of the theater are kabuki actors' wives. So you don't need to wear like them if you are not a wife of a kabuki actor.
|Koshiro's wife and Somegoro's wife|
|Danjuro's wife and Ebizo's wife|
At sumo tournaments, you may see beautiful kimono women sit and watch sumo behind wrestlers.
Most of them are madam of bars wrestlers often visit.
Most of customers are like below. But be careful, they always watch what others wear.
When you go to bathroom at the theater, there is always a long line. After you finish your job and get out from a restroom stall, somebody must say from your behind.
"Your tare ( obi's trail) is rolling up!"
Don't be shy or nervous. Just turn around to her and reply quietly. "I know ma'am, I will fix it after I wash my hands"