Premise
After the success of the original 13 idols, the president of 765 Production gives the Producer a new project: the 39 Project (pronounced sankyuu, or "thank you"), consisting of 39 girls. Helping the Producer is a new secretary, Misaki Aoba.
Gameplay
Live
The Live (ライブ Raibu) rhythm game plays similar to THE iDOLM@STER Cinderella Girls Starlight Stage. There are different difficulties for songs; for unit lives: 2 Mix, 4 Mix, 6 Mix and Million Mix (2M, 4M, 6M, MM for short), for solo lives: 2M and 2M+. Players can also watch the MVs for any song. The player needs energy for playing the songs. 2M costs 15 energy, 4M costs 20, 6M costs 25 and MM costs 30. For solos, 2M costs 15 and 2M+ costs 25.

The five possible judgments in the game, sorted from best to worst.
In a Live, players tap notes in the rhythm of the background music. Different kinds of notes will be brought in, with each having a different method of how each icon must be hit. Such notes include simply tapping the icon, tapping and holding down the icon, tapping and flicking a certain direction, tapping two icons simultaneously, and tapping and sliding a certain direction. The amount of notes can change by song and difficulty.
After tapping a note or flicking a flick note, the player will get a rating of Perfect, Great, Good, Fast, Slow, or Miss, depending on how accurately the note was tapped or flicked. Getting a Fast, Slow, or Miss resets the current combo to 0 and will decrease the player's life bar.
To clear the song, the player must not let the life bar reach 0 while playing until the end. Getting Goods and above (e.g. no Fasts, Slows, and Misses) in a single song results a Full Combo, and getting only Perfects results in an All Perfect.
Oshigoto (Work)
By using 20 energy, the player can do Oshigoto (お仕事 Oshigoto), or Work, and select Princess, Fairy, Angel or All type work; upon selecting, a random girl from that type (or any type from All) appears, and the player gains affection and fans for her, alongside rewards. Occasionally, a communication with the girl will appear and the player will get extra bonuses based on dialogue choices.
Fureai (Interaction)
The player can also navigate the theater and offices to find girls to fureai (interact) with. If a girl has a "..." bubble over her head, this will reward the player with items, affection and fill the producer gauge. Idols can also interact with each other. Sometimes an idol spontaneously get closer and talk to the producer/player. Finding the right idol to interact with is key to unlocking new main story commus.
Idols
The following idols are available for produce in the game. 52 idols are divided into three categories: Princess, Fairy, and Angel. All 50 idols that appeared in THE iDOLM@STER Million Live, and two new idols appear. Four additional idols appear in the Ex category, although they have only SR cards. In total, there are 56 idols in all four categories.
Princess Idol
- Haruka Amami
- Yukiho Hagiwara
- Makoto Kikuchi
- Hibiki Ganaha
- Mirai Kasuga
- Kotoha Tanaka
- Minako Satake
- Matsuri Tokugawa
- Yuriko Nanao
- Sayoko Takayama
- Arisa Matsuda
- Umi Kousaka
- Iku Nakatani
- Emily Stewart
- Kana Yabuki
- Nao Yokoyama
- Noriko Fukuda
Fairy idols
- Chihaya Kisaragi
- Iori Minase
- Takane Shijou
- Ritsuko Akizuki
- Shizuka Mogami
- Megumi Tokoro
- Roco Handa
- Tomoka Tenkubashi
- Shiho Kitazawa
- Ayumu Maihama
- Chizuru Nikaido
- Mizuki Makabe
- Rio Momose
- Subaru Nagayoshi
- Momoko Suou
- Julia
- Tsumugi Shiraishi
Angel idol
- Miki Hoshii
- Yayoi Takatsuki
- Azusa Miura
- Ami Futami
- Mami Futami
- Tsubasa Ibuki
- Elena Shimabara
- Serika Hakozaki
- Akane Nonohara
- Anna Mochizuki
- Hinata Kinoshita
- Konomi Baba
- Tamaki Ogami
- Fuka Toyokawa
- Miya Miyao
- Karen Shinomiya
- Reika Kitakami
- Kaori Sakuramori