There are so many great places around Sydney doing interesting things with high-end Japanese. One of my favourite restaurants in the entire city who do phenomenal Japanese food is Ume, which doesn't get enough love in the food community imo. Also Sokyo at Star is utterly incredible.
If you don't want to spend hundreds but still want a lovely atmosphere, Wagaya Tapas in Newtown is an excellent choice. You order at your table on iPads and the lovely polite staff bring it to you with a smile. The food is beautifully presented, and they also have a huge range of Sake and Shochu for the full experience.
Love the exuberant 'Irasshaimase!' when you enter - it's Japanese for "Welcome to our store!"
I haven't been there yet, but have been wanting to try Sapporo in Crows Nest because they have a separate, entirely gluten free menu. Not an easy find when it comes to Japanese food!