"Triangle," a three-member co-ed K-pop group that once dominated the music scene, disbanded overnight after being caught up in an unexpected scandal.

Twenty years later, leader Hyeon U receives an offer to perform on stage as "Triangle" for a chance to make a comeback and sets out to find the other members and seize the opportunity. "Even if war breaks out, we're going on stage today no matter what!" Hyeon U, who is now a struggling TV personality, Do Mi, who is married into a rich family, and Sang Gu, who is drowning in debt from his solo album releases, somehow reunite and head to the concert hall. But the situation spirals out of control when YGP, the CEO of their former agency with whom they share a bitter history, and Seong Gon, the "Prince of Ballad" and former rival of "Triangle," also appear.