ST☆RISH, an idol group that made a sensational debut with "Maji LOVE 1000%", composed by Nanami Haruka, an aspiring composer, while they were students at the performing arts school Saotome Academy. They were working hard every day together, aiming to become top-class composers and idols. Then one day, their agency president, Shining Saotome, asks them to take the "Master Course" to further their growth. And there, the highly individualistic idol group QUARTET NIGHT appears as their instructors!