Tsugumu Ichimonji, a world-renowned high school–aged bodyguard, transfers to a Japanese high school on a covert assignment. His mission is to protect Himeru Kokoro, the daughter of a wealthy magnate, without her knowledge. One day he follows her to the rooftop and witnesses a wall of flames and a giant dragon, with Himeru standing in the middle of it. She casually reassures him that she is immune to fire. Himeru is the reincarnation of a hero from another world, and Tsugumu swears to keep her secret. But her secrets do not stop there. Each new revelation pulls him deeper into a chaotic mix of school life, fantasy, science fiction, spy action, idol culture, robot battles, courtroom drama, horror, and magical‑girl antics. As a short‑range‑teleporting delinquent named Majima appears with a personal grudge against Himeru, the Galactic Empire Republic’s radical faction launches a large‑scale invasion with a giant humanoid robot. The story later reveals that Himeru is also a phantom‑beast protector; she, Tsugumu, and Majima shelter a phoenix while fending off demi‑human hunters. Tsugumu is then forcibly transported to the other world of Sarainen, where he is brought before a deity. Over the course of the series, Himeru’s secrets expand to include her former identity as a goddess, and the final arc pits the group against the former goddess Shiruta and the manipulative mage Mone‑gata from the original hero’s party, whose true motives span worlds. The series concludes as all of Himeru’s layers of secrets converge.