Anyone who has lived in Japan long enough eventually finds about the Takarazuka Revue Company（宝塚歌劇団）, the all-female musical troupe that has pulled out all the stops to entertain fans for over a century. As an English teacher, I've met students who have been huge fans of Takarazuka and there was one short stint with a teenager who aspired to enter the exclusive academy to become a performer. Her mother was also a huge fan so their house was absolutely covered in posters with their favourite stars on the walls. If I'm not mistaken, the Takarazuka fan shop is located underneath the Imperial Hotel (which I now understand is undergoing a major renovation which will take years to complete) in Hibiya, Tokyo near the hall where the troupe performs when it's in the capital.
Am I a fan? Not really. Takarazuka is a bit too lavish for my tastes but a good friend and I were walking through the area one Saturday night, when we just happened to come across a very fascinating sight of the fans waiting for the top star to come out of the hall for a greeting and a handover of bouquets of flowers. The fascinating part was that it was all done silently as it is always done. We could've heard a pin drop on the pavement.
I'm not sure when I first heard "Mon Paris" but I think it was probably an episode of NHK's "Uta Con"（うたコン）since I know that Takarasiennes, past and present, have come onto the show over the years. Also, I am uncertain whether this is an official theme song for the troupe but since it seems to have been performed a lot over the decades, perhaps it is. It does make sense thematically because Paris and France have been favoured settings for the troupe's plays.
From what I could glean from the J-Wiki article for "Mon Paris" is that it began as the first grand revue in Japan by the Takarazuka in September 1927. Takarazuka playwright Tatsuya Kishida（岸田辰彌）was behind it all, and a couple of years in 1929, he even came up with the lyrics for a song under the same title while Kyo Sakai（酒井協）, a Takarazuka composer provided the jaunty melody. For the above version, a student from the Flower Troupe, Miyako Nara（奈良美也子）, performed the song. A single was released from two companies (one was Columbia Records) and it became a huge hit.