The world believes SI-VIS is just a wildly popular co-ed musical group, captivating audiences across the globe with their electrifying performances and undeniable talent. Led by the charismatic队长 YOSUKE, their concerts generate an unprecedented level of fan fervor. What the public does not see is that this fervor is a vital resource. SI-VIS is, in truth, a clandestine team of heroes, harnessing the collective emotional energy, known as Soul Power, from their live shows to fuel their battles against a catastrophic threat.

That threat is the Mirage, a mysterious spatial phenomenon that generates a phantom copy of a real city within a dimensional rift. If not stopped, this Mirage will collapse, erasing the original city and all its inhabitants from existence. The architects of this devastation are the XENOS, enigmatic beings from another realm who view humanity as little more than insects to be exterminated.

The story follows Kyoya, a bright-eyed and athletically gifted high school student from Aomori who harbors a deep admiration for his cousin, YOSUKE. Driven by this dream, he travels to Tokyo to audition for SI-VIS. Upon arriving in the bustling streets of Shibuya, he encounters a mysterious, quiet girl named Nagi, who shows an unusual interest in him. Through her, Kyoya stumbles upon the group's secret identity and witnesses their desperate struggle against a Mirage firsthand. When YOSUKE tragically falls in battle against the XENOS, the group is left shattered. Inspired by his cousin's sacrifice, Kyoya accepts the heavy mantle and is thrust into the role of SI-VIS's new frontman, vowing to protect the world YOSUKE loved.

Kyoya must quickly adapt to a team of powerful but difficult personalities. There is Siren, the group's prodigious but lethargic ace and composer who lives on junk food; μ, a seemingly cute mascot who is secretly a calculating, social-media-obsessed schemer; Souji, a strict and serious performer with a large male following; and June, a gentle and prince-like heartthrob who keeps an emotional distance from everyone. Each member copes with the loss of their leader in their own way, and Kyoya struggles to earn their trust and prove he is more than just YOSUKE’s replacement.

As Kyoya integrates into the team, they face escalating threats from the XENOS, including the rational Krios and his protective twin Lukos, who are curious about humanity, and the ruthless leader Apollo, who sees Earth as a plague. Kyoya also enters Harmonia Entertainment’s special school, where the group manages their public image as idols while secretly training for combat. A major arc follows the discovery of a painful secret: June had a twin brother, a former SI-VIS singer whose existence was erased from memory after a failed mission against the XENOS. This revelation deepens the group's trauma and the stakes of their fight. As they clash with the XENOS over the fate of the world, Kyoya must harness his own unique potential as a singer and a hero, culminating in a confrontation that forces the team to sacrifice everything for the future of music and humanity.