According to a report today in the Shinano Mainichi Shimbun, E7 trains will begin revenue operations on the Nagano Shinkansen route between Tokyo and Nagano from March 15. Three 12-car E7 trainsets will initially be introduced, providing 7 roundtrip services/day. The services will continue to use the Asama monicker used by the current E2 trains. With this introduction, 1/4 of all Asama services will be run with E7 trainsets (the regular schedule on this route sees 28 r/t a day). As the E7 trainsets are 12 cars, with a passenger capacity of 934, they provide 1.5 times the passenger capacity of the current E2 Asama trainsets, which have 630 seats.
http://www.shinmai.co.jp/news/20131220/KT131220ATI090006000.php