Maps are protected by Japanese copyright law. Map publishers like Zenrin, show their copyright guidelines on the website and clarify their maps are protected by copyright law.
According to Google guidelines, all uses of Google Maps and Google Earth content have to provide attribution to both Google and its data providers.
However, maps images are often used on website, blogs, or somewhere else improperly and illegally.
Recently, Iwate prefectural government office of Japan anounced that they had used maps images such as from Google or the Geospatial Information Authority of Japan (GSI) improperly. Maps images in question were delated.