Sachiko Koshimizu is a fictional character from the anime series THE IDOLM@STER Cinderella Girls. She is known for her overly confident personality and often refers to herself as 'the cutest in the world.' Despite her arrogant demeanor, Sachiko is hardworking and determined to prove her talent as an idol. Her character is a playful parody of the idol industry, where she constantly seeks attention and admiration. Sachiko's role in the series is to provide comic relief and to showcase the diverse personalities of idols within the Cinderella Project, ultimately winning fans with her charm and dedication.