>>279809196The manga has this ongoing storyline where the girls are first trying to get any job they can and then after they get popular from a viral video, they're trying to debut at a big live with the older girls. Parts of this storyline still exist in the anime, but they are executed differently and most of the drama is removed because they didn't have enough episodes to work through it.
Most of the story arcs for the idols are new or are combinations of different things that happened in the manga. Except Momoka, whose arc is basically the same in both. For example, in the manga Kaoru's arcs are with Mai and Haru and are about cooking (with vegetables she doesn't like) and painting. In the anime, however, Kaoru's episode is an adaptation of the Chika introduction/trip to the beach from extremely early in the manga, with aspects of the "cooking with vegetables she doesn't like" plotline included to make it more Kaoru themed. This was probably done to emphasize all the girls sleeping at the end, which is a direct adaptation of one of the cutest scenes in the manga.
So it's interesting, some scenes are direct adaptations of specific imagery in the manga, but the chronological order is all over the place and lots of details are changed. Like in the opening episode, the scene in the hallway with the girls picking on ManletP and then Nina and Kaoru begging him to stay is a 100% direct adaptation, but the scene before it where the girls run into P and Risa calls him a lolicon is nowhere to be found in the manga, and Risa doesn't ever call him that to my knowledge.