Based on COLOPL's school action role-playing game. Set in the year 2045. The world has been contaminated by Irousu (mysterious invaders who suddenly appeared), and humans find themselves restricted and contained. Standing boldly against these invaders are ordinary girls everywhere, without a powerful army or even weapons. The Shinjugamine Girls Academy is a school for these "Hoshimori" (Star Guardians) destined to fight the Irousu. The player is assigned to this academy to train the girls and take back the contaminated Earth. And so, once again, the chimes echo through the sun-strewn schoolyard to mark the beginning of classes today...

My Melody arrives on Earth much to the surprise of her rival Kuromi. Together with one of the junior high school students, Yumeno Uta, they decide to protect the dreams of the people with the help of magic.

The anime's story will start where the third season left off, at the competition for who will open the Triple S international sporting event. Raging Entertainment's HE★VENS idol group had hijacked the competition between QUARTET NIGHT and ST☆RISH, causing chaos. However, after the QUARTET NIGHT members suggest a certain idea, the three groups aim toward a new stage, with HE★VENS swearing to get their revenge on the other two groups.

Throughout Shibuya, a series of murders dubbed the "New Generation Madness" gained widespread attention As these crimes gained infamy, they became a hot topic of discussion among the people of the area. Nonetheless, these "New Gen" murders do not capture the interest of Takumi Nishijou, a high school otaku who frequently experiences delusions and feels that he is constantly being watched. Having no concern for the real world, Takumi spends his time playing online games and watching anime. However, his ordinary life is disrupted when he receives a horrifying image of a man staked to a wall from a user named Shogun. After calming himself at an internet cafe, Takumi sees the exact same murder scene as the image portrayed happen right before his eyes, along with a pink-haired girl covered in blood calling out his name. Conflicted with the nature of reality, Takumi finds it difficult to judge where to place his trust as he gets caught up in the "New Gen" murders, believing that the murderer is out to get him.