When she was younger, Arisa learned the piano, and she attended the same music school with Tae and Rei, where she was part of the Pianist Course.[2] However, she ended up quitting because she didn't have any motivation to continue, and also because she had to study for middle school exams.[3] When she befriended Kasumi and heard about her plans to start a band, she picked it up again so she could be the keyboardist for Poppin'Party.

Ran is the only child of the masters of a flower arrangement school that dates back to over 100 years ago, and which her father currently owns.Ran has short black hair with her short bangs partially tucked beneath her forelocks, one of which is dyed red. She has partially sharp dark pink eyes.

Rinko is a very talented keyboardist who has played the piano ever since she was 5 years old, and prior to joining Roselia, had even won in multiple music contests. She started taking piano lessons after her mother took her to watch a concert. However, she stopped participating in contests after she failed during a big one because of stage fright

Minato Yukina is a first-year student at Yotsuba Women's University and the leader of and vocalist for Roselia. She is a powerful vocalist, sparking the admiration of the other Roselia members, as well as the other people around her. Yukina has sharp, gold eyes and long silver hair worn loose with some type of black butterfly hairclip decoration. Her long forelocks rest over her shoulders, and her bangs just reach her eyes.

Soyo has long, waist-length light brown hair and grayish-blue eyes, often supporting a gentle expression on her face. Her original band outfit consisted of a white turtleneck sweater with black cuffs, a black belt with a silver buckle, and a deep blue skirt with a long outer mesh layer. Her shoes are black with a chartreuse yellow cross on each. In her casual outfit, she wears a blue-white blouse with short, puffy sleeves and a frilly neckline, a cream-colored skirt with small flower patterns, and a thin brown necklace with a star charm on it.

Maruyama Aya is a first-year student at Yotsuba Women's University and the leader of and vocalist for Pastel*Palettes. She also works part-time at the fast-food store with Kanon. Aya has always admired idols ever since she was young, and the reason she wanted to become an idol was because of the idol group Marmalade's lead, Ayumi. Aya then spent three years being a trainee idol before she was chosen to become the lead singer for Pastel*Palettes.

Ever since they were young, Hina has always bested Sayo in everything, in simple things such as seeing who can swing higher in the playing ground's swings, to more complex things like test scores. Whereas Hina can master new skills with ease, Sayo requires a great deal of information before she can even begin to practice. As a result, Sayo formed a severe inferiority complex towards Hina. One of Sayo's main reasons for starting to play the guitar was because "it was something Hina wasn't doing".

Mashiro was first shown in Girls Band Party! Main Story 2 Chapter 8. Poppin'Party finds her at CiRCLE and recognizes her as the girl they talked to after the mini-concert (which is shown in Chapter 3 of Morfonica's First Band Story). Kasumi and the others approach her as she looks at her flyer she made for recruiting band members before taking it down and saying she didn't find being in a band as enjoyable as she imagined it would be. Feeling dejected, she states she'll never come back to CiRCLE, goes away and leaves Poppin'Party in a bewildered state.