Shion Amemiya is a student at Seisho Music Academy who participates in the Play Creator Program.

She is the playwright for Class B's performance of Starlight, always seen with director Kiriko Masai and she is presumably responsible for Nana Daiba when she takes on the role of trainee playwright.

The stage emulates life and compresses it, setting free skills learned over lifetimes in brief but dazzling displays for the amusement and judgment of others. For the performers, it is the ultimate risk, and some will rise while others must fall. Nowhere is this truer than at the Seisho Music Academy, where music, dance and real weapons all come into play in the creation of the next great Star. Karen and Hikari’s destinies have been linked since a childhood promise, but their journeys here have taken very different paths. Now, after Hikari leaves, Karen must discover who she is without her opposite, while Hikari must rediscover her own course.<br>
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(Source: Sentai Filmworks)

The franchise centers on "Starlight" — the song and dance revue troupe loved throughout the world. Karen and Hikari make a promise with each other when they're young that one day they'll stand on that stage together. Time passes, and now the girls are 16 years old. Karen is very enthusiastic about the lessons she takes every day, holding her promise close to her heart. Hikari has transferred schools and is now away from Karen. But the cogs of fate turn, and the two are destined to meet again. The girls and other "Stage Girls" will compete in a mysterious audition process to gain acceptance into the revue.
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(Source: Anime News Network)

The story of the nine stage girls from Seisho Music Academy and their daily lives before the TV Anime!