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?
"The more you attack, the more energy he absorbs. And now he is immune to celestial energy. He can absorb it without repercussions. I can't help you Tsuoma. I'm weak compared to my elder siblings." Thalia moaned. Tsuoma knew he had to think for himself. How would he defeat a foe which seemed undefeatable? What weakness could he exploit? Celestial energy was the strongest type of energy in this world. And one strange being just absorbed it without feeling any repercussions. There were a lot of ways he could defeat Neil but none had come to Tsuoma's head. He started thinking about some movies he had watched and remembered one that had an energy absorber as a villain. He had watched the movie at a theatre as it was recommended by Teruki back then.