Suzaku Akai's pet cat, who he is almost never seen without. Like Nyako, it's voiced by Masuyama Takeaki in songs and stories. Its real name is Nyankii.
Nyako dislikes Genbu Kurono due to Genbu having a cat allergy, but they get along through their mutual respect of Suzaku. It appears to be able to communicate with Suzaku. Despite being a cat, it is very performative and shows itself off with unusually self-aware poses; Suzaku says its reason for becoming an idol is to find its estranged family members, so it presents itself to society in order to be seen.
Suzaku Akai's parents. Both are professional wrestlers who want Suzaku to become a pro wrestler as well, despite Suzaku wishing to stay with Genbu and Shinsoku Ikkon forever. Because they both work, Suzaku was often left around other adults when he was younger.
Ryo Akizuki's cousin who is an idol at 765 Productions. She is a smart and hardworking idol who formerly worked as an intern at the agency before debuting herself.
During the events of Dearly Stars, she introduced him to 876 Productions, where he worked as a female idol. She also introduced him to Makoto Kikuchi, another 765 Productions idol who became Ryo's friend.
The president of 961 Productions, whom Jupiter formerly worked for during the events of THE iDOLM@STER 2. Jupiter left his agency after Touma found out that he was using illicit methods to push the unit's popularity.
Seiji Shingen's former friend who was in the Japan Self-Defence Forces with him. He died in the middle of a terrorist attack while protecting a child. Seiji wears his dogtag as a sign of respect, and has fond memories of making curry with him. Their curry contained chocolate, giving it its unique flavor.
The son of Kyoto's mayor. During middle school, Genbu Kurono scored higher than him in the final exam, so he had Genbu expelled and forced him to leave Kyoto. Later on, he encountered Genbu again in Yokohoma.
Kei Tsuzuki's former friend who he met in Berlin as a child. The so-called Angel was a musician who performed in a hall near Kei's home; this was where they met, sparking a friendship that would heighten Kei's interest in music. One day, the angel suddenly left Berlin as they had supposedly gained a successful music career.
Ryo Akizuki's former unitmate from when he was in 876 Productions during the events of Dearly Stars. Ai is a passionate and loud girl whose mother was once the country's top idol. Eri is a shy, quiet girl who became an idol after gaining fame online as her net persona.
A policeman who works at a police station near Ouken High. He formerly worked with Hideo Akuno while the latter was a police officer. Shinsoku Ikkon, who know him from frequently walking by the station after school, refer to him as 'old man'.