Should you get tired of French food at some point (anything can happen!), Paris has its fair range of Japanese options to choose from.
Beware that so many sushi bars are actually converted Chinese eateries--an indication that sushi must be more lucrative (or more trendy) than Beijing duck at this point.
Second, as elsewhere, sticky rice covered with thin strips of uncooked fish can get expensive. Fortunately, since the '70s, when Japanese banker-types first moved to Paris, Paris has built a solid stable of Japanese restaurants.
Tokyo-on-Seine has settled just north of the Louvre, on and around rue Sainte-Anne. The prices are sweet, and the range of cuisine is unexpectedly broad--from sushi to fried noodles, from bbq to udon etc.
For its okonomiyaki and udon, I am partial to Aki, at 11 bis, rue Sainte-Anne--the most subtle, in short the best.
A parting word, for people who like to know what's behind the scenes--one man, a Japan-born Korean, is said to be behind every other establishment on rue Sainte-Anne. Tokyo-on-Seine is thus, well, a Korean creation.