Television audience ratings in Japan can be obtained in a number of ways: 1) people (e.g., employees) who have access to inside formation from the Japanese ratings research firm
Video Research Ltd., who then may post TV audience ratings on their blogs, message boards like 2ch, etc.; 2) contacting Fuji TV and NTV by telephone a day or so after programs have aired on their station to get the TV audience ratings (this reportedly cannot be done with NHK, TBS, TV Asahi, TV Tokyo); 3) getting TV audience ratings for shows two or more weeks after they have aired at the National Diet Library; 4) news media reports; 5) animation company press releases; 6) Video Research Ltd.'s official website (usually just the top 10 in various categories {news, animation, movies, sports, etc.}); and whatever else I have left out.
Recently, someone
posted at 2ch the TV audience ratings of the first six to eight episodes for a number of late night anime series which debuted during spring 2007 in Japan. I cannot vouch for their accuracy, but presumably they got the data from the National Diet Library.
Note: As a NTV program, Claymore's TV audience ratings (episodes 1-11 so far) can be independently verified by phone and posted on threads at message boards like 2ch.
Late Night Animation Program Television Household Audience Ratings in the Kantou Region (Tokyo, Yokohama, Kawasaki, Saitama, Chiba, etc.) of Japan
El Cazador de la Bruja 2.1% 1.8% 0.9% 0.6% 1.4% 1.4% 0.9%
Kissdum ENGAGE PLANET 1.9% 2.2% 1.7% 1.0% 1.2% 1.6% 1.5%
Claymore 2.0% 2.2% 2.3% 1.8% 2.5% 1.1% 2.0%
3.0% 2.1% 1.9% 2.5%
Over Drive 1.9% 2.0% 1.4% 0.9% 1.1% 1.2% 1.2%
Shinkyoku Soukai Polyphonica 1.1% 0.6% 0.3% 0.7% 1.0% 0.2% 0.7%
Nagasarete Airantou 2.3% 1.9% 1.5% 2.4% 1.5% 1.2% 1.3%
Kishin Taisen Gigantic Formula 1.8% 1.6% 0.7% 1.7% 0.9% 0.6% 0.9%
Ookiku Furikabutte 2.9% 1.8% 2.2% 2.9% 3.0% 3.2%
Kaibutsu Oujo [Monster Princess aka Princess Resurrection] 2.4% 1.2% 1.6% 2.6% 1.7% 1.9%
Koutetsu Sangokushi 0.8% 1.4% 0.6% 0.8% 0.2% 1.0% 0.7%
DARKER THAN BLACK - Kuro no Keiyakusha 2.6% 1.9% 1.9% 1.2% 1.4% 1.3% 1.8%
Romeo x Juliet 2.2% 1.2% 1.1% 1.3% 1.1% 1.6%
Heroic Age 1.3% 2.0% 1.9% 1.3% 1.2% 1.0% 0.8% 1.7%
Seto no Hanayome 2.2% 1.6% 1.6% 0.9% 1.2% 1.4% 1.6%