Glass Mask (ガラスの仮面, Garasu no Kamen?) is a long-running shōjo manga by Suzue Miuchi, serialised in Hana to Yume from January 1976, and collected in 42 tankōbon volumes as of 2006. The story has also been adapted into anime and a live action television series. As of 2006, the collected volumes had 50 million copies in Japan, making it the second best-selling shōjo manga ever. The title refers poetically to the mask of faces that actors wear - while expressing emotions that are not their own, the mask they wear (their acting) is as fragile as glass. If the actors are distracted, their mask will "break" and show on stage the actors' true feelings.

After not publishing a new chapter in the story for more than two years, Miuchi re-lauched the series in Hakusensha's Bessatsu Hana to Yume (別冊花とゆめ) magazine in July 2008. The story continues from where it left off in volume 42.

Source: Wikipedia