In the future, digital viruses known as Oracles have spread and infected people called Fector, causing them to turn into mythical creatures. To combat this, humanity developed a vaccine that temporarily gave some individuals animal or insect traits in order to fight back against the Fector. One summer day, Sogami Eiris childhood friend who had disappeared reappeared before him, and he found himself caught up in an incident involving the Fector. Along the way, he discovered the truth about his own existence, which shook his relationship with his sister and turned him into a "king" to protect her. This is the story of a boy who risked everything for the sake of saving one girl.