The story begins with Amamiya Sota, an eighteen-year-old adventurer of six years, reaching the final chamber of a notoriously difficult underground labyrinth. He has single-handedly defeated a stone golem and stands before the "Paradise Gate," a legendary portal said to lead to a dream world. Sota discovers that to open the gate, he must use "True Magic," a spell requiring extensive academic study at a magic academy, something he, having started adventuring at ten, has never pursued. His hopes are crushed, and as he despairs, the golem he defeated begins to regenerate. Pursued by a growing number of golems, Sota uses the forbidden, one-time-use teleportation magic, "Escape," to flee the labyrinth.
Determined to learn "True Magic," Sota decides to enroll in the Mariannes Kingdom's First Magic Academy, the most prestigious institution in the kingdom, where the Adventurer's Guild headquarters is located. The Adventurer's Guild categorizes quests into five ranks: Normal, Bronze, Silver, Gold, and Platinum, based on difficulty and danger. Sota, without any preparation, passes the academy's practical entrance exam with a perfect score.
Upon arriving for enrollment, Sota meets the eccentric and physically imposing Headmaster Regis and his sharp-tongued secretary, Rouge. Regis reveals that the academy, recently made co-educational, has a significantly higher female student population. Later that evening, as Sota leaves the academy, a large bird snatches his sword. While attempting to retrieve it, Sota falls through the roof of a public bathhouse and lands in the women's bath, accidentally touching Princess Liena Marianes.
The ensuing commotion leads Sota back to Headmaster Regis's office. Liena demands Sota's expulsion, but Regis proposes a duel between them, with the loser obeying the winner. Liena, ranked fifth in the academy, confidently accepts, intending to send Sota to a prison known as the "pigsty."
The next day, the duel commences in a grand arena, drawing a massive crowd. Before the match, Liena's bodyguard captain, Elisa, attempts to stop Sota but is easily defeated. The duel begins with Liena unleashing powerful lightning magic, demonstrating her talent as a "prodigy of thunder" and her ability to use un-chanted magic. Sota counters with his own wind-based "Sickle Wind" and reveals he is using "Hard Body" magic to harden his physique. Liena then activates "Magic God Armor," transforming into a more powerful form and equipping a rapier. Despite her enhanced abilities, Sota's defense proves formidable until Liena's "Thunder Pork Machine Gun" breaks through his "Hard Body."
However, Sota recovers and uses his wind magic to deflect Liena's attacks. The duel escalates, with Liena unleashing increasingly powerful lightning attacks, including a homing "Thunder Lance." Sota, seemingly overwhelmed, is hit by multiple lances. Liena then conjures a massive thundercloud and unleashes "Big Thunder Bolt," creating a crater where Sota stood. To everyone's surprise, Sota emerges, albeit exhausted. He then reveals his true strength, easily overpowering Liena. Just as he is about to finish her, Liena uses a sleep spell, "Schlafen," which unexpectedly incapacitates Sota due to his extreme susceptibility to hypnosis. Liena is declared the winner.
Suddenly, a spatial rift opens, and a massive Minotaur, claiming to be from the "Beast World," emerges, intending to conquer the human world. It attacks Sota, who is still asleep, and then turns its attention to Liena. While the academy staff, including Regis, Rouge, Elisa, Mia, and Cathy, fight off invading goblins and other monsters, Liena attempts to fight the Minotaur but is outmatched. Just as the Minotaur is about to strike Liena, Sota awakens and intervenes.
Sota, now radiating a dark aura and wielding his black sword, easily defeats the Minotaur, revealing himself to be a "Platinum Rank Adventurer" known as "Dragon Slayer Sota," who single-handedly defeated a colossal dragon a year prior. The Minotaur, revealed to be a subordinate of the dragon Sota killed, is enraged. After a fierce battle, Sota defeats the Minotaur with a devastating attack.
With the immediate threat neutralized, Liena, impressed by Sota's strength and realizing he isn't a bad person, asks to join his party. Sota, surprised, accepts her request.
