We are also taking a cruise out of Singapore, leaving in October. We have not been to Tokyo either, so we decided to do a layover there for three days as an opportunity to see the city. We booked our flight as a multi-city and the cost was not that much more than a direct to Singapore. I realize this doesn't answer your question, but you might want to consider it if you have enough time. I figured we would probably only be in the Asia once, so might as well see Tokyo!