On a cold night, idol group TRIGGER reunite at a bar to celebrate the anniversary of the day they started working together. Two years prior, Ryuunosuke Tsunashi leaves his Okinawan home and heads to Tokyo, hoping to become an idol and pay off his father's debt. While waiting for the manager, he is instead picked up by Gaku Yaotome—son of Yaotome Productions' CEO and Ryuunosuke's future co-worker—and they go to meet the mysterious Ten Kujou, the last member of the group.

Gaku wants to confront Ten, as he is dubious of Ten's position as the center of the group. Fortunately, with Ryuunosuke's help, the three of them are able to hit it off, and thus TRIGGER is born. However, there still remain obstacles they have to overcome before their rise to fame.

In the present day, their rivals IDOLiSH7 also have their own set of problems. From planning what to do on their free days to resolving a long-lasting dispute, they are ready to work together and face these problems head-on.