Interesting name...although it'll be challenging to monetize, and will require some serious work.
If you're prepared to make a lot of calls and explore hitting some of the larger namesake entities such as Nippon Life, the JX Nippon Mining Company, Nippon Gohsei, NTT or Nippon Express for example (although i'm sure there are many more smaller companies with Nippon as a name)....you might have something that resembles a pot on the other side of your rainbow. Either that or change it up and rely on the literal meaning of the word and target major players of the international travel industry who are entering, establishing or growing tourism based services for Japanese people to tropical sun soaked destinations.
To develop your own site with this domain, in my opinion would be difficult....it's really only the Japanese people who refer to Japan with this name....and it clearly sounds like a Japanese name.
The .io is a strong emerging extension, but costly to maintain and the right name combination needs to be found or you risk losing money the longer you hold the domain. Depending on where you registered, those annual costs are anywhere from 32 to 90 bucks. Hold the domain for 2 years and unless you sell for a profit quickly, you're soon at a risk of barely breaking even. Unless its a game-changer domain name, by year 3...chances are it'll be at a loss....and the deeper that hell hole can get as the years linger on and more TLDs are launched.
Food for thought, but what the hell do I know.
Good luck with your efforts.