Naisho no Tsubomi (ないしょのつぼみ, Naisho no Tsubomi? lit. Secret Tsubomi) is a Japanese shōjo manga authored by Yuu Yabuuchi, and published by Shogakukan. As of 2008, 3 volumes have been released in Japan. An OVA anime for the series was released on the 24th of April, 2008. A second OVA episode will be released in June, 2008.

Source: Wikipedia