The U149 in the title refers to the aspiring idols at the center of it all: These small girls are ready to make it big! All under 149 centimeters tall, this group of aspiring pop idols dream of performing for thousands of people. But with zero experience, they’ve got a lot of work to do. Not to mention there’s a distractingly cute prince in town! With the help of their rookie producer, who’s just as short, can they stay focused and make it to the top? 
(Source: Crunchyroll, edited) 
 

Note: Announced during DAY 2 of "THE IDOLM@STER CINDERELLA GIRLS 10th ANNIVERSARY M@GICAL WONDERLAND!!!" final tour concert, a TV anime adaptation of the spin-off manga THE iDOLM@STER Cinderella Girls: U149.