After being betrayed and killed by his best friend, Tsuoma Sadeo is reincarnated into a fantasy world where humans and magical creatures coexist. Armed with his indestructible sword and immense magical powers, he becomes a formidable sword mage. However, his new life takes an unexpected turn when he is met by the Princess of Straterfall Kingdom, his summoner, who has a crucial mission for him. A powerful demon, Urea, has possessed the Empress of Latasha, the second most powerful kingdom, and is secretly rallying dark mages to awaken the King of Demons, Agarrat, from the abyss. A goddess, determined to prevent this catastrophe, forms an unlikely alliance with the Princess of Straterfall. Together, they summon Tsuoma and, by mistake, his friend Teruki. The two must undergo rigorous training to defeat the Three High Demons: Urea, Trezona, and Duggan. As the stakes grow higher, Tsuoma and Teruki race against time to prepare for the ultimate battle. Will their training be enough to save the world from destruction, or will they run out of time? And who exactly is the supreme one and what is his or her plan?
Tsuoma was quite surprised himself. Truly he hadn't considered the body he was inhabiting. There was something he had been meaning to know. Why was he reincarnated into the body of this person? After getting everything he needed from the leader, he went back to his room. There he conversed with the goddess. "Goddess, I want to know about my host, the owner of this body. What happened to him?"
Thalia materialised and answered. ''Find the answers yourself. Go deep into the recess of the mind and seek the hidden memories which have been in place for a long time." Tsuoma was confused. "But it's my mind and all. How can I search for his memories in my mind?" "The body remembers even if the mind is different. Meditate and unlock the secrets you seek."
Tsuoma shrugged. He breathed in deeply and sat in a meditative pose. He cleared his mind and within a few minutes he found himself in a void.