The deal isn't on their website but I walked by the restaurant today and a lady was giving out the flyers. I was going to eat there for lunch but they said it would be a 25 minute wait so I went elsewhere. Would suggest going there earlier if you don't want to wait. The deal is not valid for take away.
Check out their website for the menu but there is no lunch menu, just says that it has lunch specials from $9.90 which would make lunch from $5 which is pretty cheap for lunch in the city. Deal is available until mid August so plenty of opportunities to go by.
There's also 25% off for people going late and for karaoke after 11pm if anyone is into that.
Location: 591 George St, Sydney
Website: http://www.lantern-wagaya.com
Are they inside World Square?