The protagonist, a reincarnated individual who enjoys observing, finds himself as the Evil God Ashtar, destined to await the hero in his Dark Temple. Having waited for a millennium, Ashtar is bored and frustrated by the hero's prolonged absence. His attendant, Eurius, a seemingly young but ancient being, diligently serves him. Ashtar learns that the hero party, unaware of his existence, considers defeating the Demon Lord the ultimate victory. The Dark Temple only appears after the Demon Lord's defeat, and Ashtar's role is to confront the hero, overwhelm them, and instill fear in humanity, as per divine instruction.
During this millennium, Ashtar has continuously trained, becoming immensely powerful, far surpassing his predecessor. He observes the world using his Evil Eye, noting the uneventful period following the defeat of the latest Demon Lord. He then turns his attention to the hero, Princess Euphylia Plantagenet, who, after defeating the Demon Lord, has returned to her kingdom and enrolled in Cantabridge Academy, a school for adventurers. Ashtar, despite his immense power, suffers from a debilitating social anxiety around women, a trait he carried from his past life and which now hinders his ability to confront Euphylia.
When Euphylia and her party finally arrive at the Dark Temple, Ashtar's attempt to speak results in incoherent babbling, and his fear of women paralyzes him, leading him to be easily defeated and left for dead by the hero party. They leave, deeming him a weak, harmless entity. Ashtar, however, is immortal and quickly recovers. He realizes his weakness and, with Eurius's help, decides to enroll in Cantabridge Academy to overcome his social phobia and prepare for future encounters.
At the academy, Ashtar, now disguised as a student, struggles with his inability to communicate properly with women, often speaking in unintelligible gibberish. He befriends Euphylia, who, despite his strange speech, seems to understand him. He also encounters his subordinates, the Evil God Army's commanders, who have infiltrated the academy in various roles, including Eurius as a teacher and Jekko as a janitor. They explain their presence is to support Ashtar and that their infiltration was facilitated by the academy's head, Serina, a legendary hero.
Ashtar joins the Dungeon Club, a group dedicated to dungeon exploration, where he demonstrates surprising combat prowess by easily breaking a warrior's weapon, though his initial hesitation still causes issues. He also inadvertently creates a magic item that causes uncontrollable arousal in women who wear it, leading to embarrassing incidents with his female companions, including Euphylia and the mage Tiraisa. Ashtar, lacking sexual desire as an Evil God, is bewildered by these reactions.
The narrative also touches upon the world's history, including past Demon Lord calamities and the academy's esteemed reputation, highlighting the power of figures like Serina. Ashtar registers at the Adventurer's Guild, where his immense, undetectable power causes chaos and the destruction of a testing crystal, further solidifying his mysterious nature. He continues to navigate his new life at the academy, grappling with his overwhelming power, his crippling social anxiety, and the growing suspicion of his companions, all while secretly observing and preparing for the hero's eventual return.
