Here is a short list of newspaper article databases for Japanese newspapers:
Asahi Kikuzo II Visual: Full text access to Asahi shinbun 『朝日新聞』 (1879-present), Historical Photo Archive, containing ca. 10,000 pieces of historical photographs taken in Asia and Europe from the 1930s to 1945, and Asahi gurafu 『アサヒ・グラフ』 (1923-1945).
Factiva: Provides access, mostly to full text, to nearly nine thousand business and general news sources, including U.S. and international newspapers, magazines, and wire services; includes major Japanese newspapers such as Yomiuri shinbun 『読売新聞』, Mainichi shinbun 『毎日新聞』, and Sankei shinbun 『産経新聞』 (warning: covers only recent years).
Nikkei Telecom 21: Full text access to Nihon keizai shinbun 『日本経済新聞』 (1876/12/2-1961/12/31, and 1981/10-present), Nikkei sangyō shinbun 『日経産業新聞』 (1981/10-present), Nikkei ryūtsū shinbun 『日経流通新聞』 (1985/10-present), and Nikkei kin'yū shinbun 『日経金融新聞』 (1987/10-2008/1) is provided; it also offers English sources such as Nikkei English News, Nikkei Weekly and translations of major articles from the above-mentioned Japanese newspapers, as well as Nikkei Company Profile (30,000 company profiles) and Nikkei Who's Who (20,000 corporate executive profiles).
Nijisseiki media jōhō dētabēsu 20世紀メディア情報データベース: Indexes to magazine and newspaper articles published between 1945 and 1949 held in the Prange Collection at the University of Maryland, which originally belonged to the Civil Censorship Detachment, a unit within GHQ.
Shinbun Kiji Bunko 新聞記事文庫 (Newspaper Clippings Collection): Research Institute for Economics and Business Administration at Kobe University has developed "Newspaper-Clippings Library" which comprises 3,200 volumes of scrapbooks containing newspaper-clippings from various newspapers, including Ōsaka Asahi 『大阪朝日』, Ōsaka Mainichi 『大阪毎日』 Ōsaka jiji 『大阪時事』,Chūgai shōgyō shinpō 『中外商業新報』, Taiwan nichinichi 『台湾日日』, Manshū nichinichi 『満州日日』, and Keijō nippō『京城日報』, covering the period from 1912 to 1970. In 2000 Kobe University Library began to digitize the clippings for 1912-1943 from the "Newspaper-Clippings Library."
Yomidasu Rekishikan ヨミダス歴史館: Full text access to Yomiuri shibun 『読売新聞』 (1874-present) and Daily Yomiuri (1989-2013)/Japan News (2013/4-present). The database also provides dictionaries (Japanese/English, English/Japanese, or new words dictionaries) to look up definitions and biographies, just by highlighting any words in the article and clicking dictionary buttons
Digital Archive of Japan's 2011 Disasters (designed and maintained by the Reischauer Institute of Japanese Studies at Harvard University): An online portal to digital materials documenting the cascading series of natural and man-made disasters that began in Japan on March 11, 2011.
Pressnet: Provided by日本新聞協会, an independent and autonomous organization funded and operated by daily newspapers, news agencies and broadcasters, Pressnet offers various data and information about Japanese newspapers.