SI-VIS is a co-ed music group, led by Yosuke, shaking up the global music scene with their unmatched vocals and performances. However, they are actually heroes in disguise, battling against mysterious forces threatening the world. They convert audience energy at live performances into combat power. Luckily, the battles appear to be ordinary concerts to the public, keeping their identity a secret.

Early 2000s Tokyo. Isobe, a combatant for the evil corporation Ganglion, spends his days on the battlefield. Whether it's the "Tokyo Cedar Pollen Operation" or the "Mount Fuji Demolition Plan," he faces off in nothing but a bodysuit, only to be crushed by the hero Hopeman time and again. As he struggles under unreasonable bosses during the dawn of compliance, his story unfolds—a workplace drama dedicated to all who work, following the bittersweet life of a salaryman soldier.

Ren Homura has just moved back to his hometown of Kaminohara, but he is not able to remember much about the time he spent there other than vague flashbacks. When he retrieves his cell phone which he had sent to a shop for repairs, he finds that a mysterious game titled "Monster Strike" has been installed on it. Unaware of its purpose or how it got there, Ren decides to open it, an action that will change his life forever as he finds himself suddenly attacked by a strange man. Now trapped on the roof of his school which strangely has been designated as a "stage," Ren is shocked to see the man summon a realistic monster from the game, one that is more than capable of inflicting damage on a human. His only chance of getting out of this situation alive is by summoning the dragon Oragon, who tells Ren that he will crush the opposing monster for him. Unfortunately, it turns out that Oragon is a tiny dragon that is completely useless!

Lunia, the daughter of the Count of Persephone, was shunned by her father and treated like a tool by her half-brother, leading a lonely life. Meanwhile, she is chosen by a priest to be engaged to Hades, the head of the Duke of Khronoa family, and decides to marry into the cursed duke family. The Duke of Khronoa, feared as the "King of the Underworld," is cursed with a short lifespan if he does not marry a bride chosen by the emperor. However, Hades tells Lunia that he has no intention of loving her. In order to keep Hades alive, Lunia deceived him and spent the night with him, then disappeared without realizing that she was pregnant with his child. Seven years later, Hades somehow managed to find Lunia and tried to take her back with the child...