1. A (video) game developed by a Japanese developer.
2. A (video) game full of Japanese language.
3. A (video) game imported from Japan whether it already has been localized or not.
4. Usually all of the above.
2. Usually language means nothing when it comes to playing Japanese games.
3. IMO, some of the best places to import Japanese games are at eBay, Amazon and Play-Asia.
4. Dad, will you let me go learn Japanese so I can import and play this Japanese game developed by the Japanese developer NMK?