Self-professed "home security guard" Mahiro Oyama has not left his home in years, secluding himself in his room playing erotic visual novels. This depraved lifestyle causes his prodigious sister, Mihari, to worry about his well-being. In hopes of solving this problem, she devises a plan to rehabilitate him back to normalcy. The first part of Mihari's plan is to concoct a medicine that changes her brother's biological constitution into a bona fide female, much to Mahiro's vehement dismay. Stuck in this predicament, Mahiro has no choice but to live out his life as a cute girl until the effect wears off—if it ever does.

After foiling a world-threatening plot, Shigeo "Mob" Kageyama returns to tackle the more exhausting aspects of his mundane life—starting with filling out his school's nerve-racking career form. Meanwhile, he continues to assist his mentor Arataka Reigen and the office's new recruit, Katsuya Serizawa, in solving paranormal cases of their clients. While continuing his duties, Mob also works on gaining more independence in his esper and human lives, as well as trying to integrate better with the people around him. However, new supernatural and ordinary challenges test Mob’s emotional stability and force him to confront the realities around him. As he strives to continue forward on the path to maturity, Mob must resolve his emotional crises and reassess the naivety he has held on for so long.

Second part of Dungeon ni Deai wo Motomeru no wa Machigatteiru Darou ka IV.

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...