Kenshi Raito, the son of two divorced parents, at the age of 16 is now going to Japan to live with his mother. At the airport, he meets Yuga Higitsune, a temperamental girl with a fiery personality. She is angry and edgy due to having to wait for her Uber to pick her up. He offers her a ride with his uber instead and she accepts. He later meets her again at the grocery store where he works and assists her in different duties. One night on his way home, Kenshi hears screaming from nearby woods. He finds Yuga being kidnapped and dragged towards a strange cave by group of men in strange clothing with a black dragon crest on their back. He attempts to rescue her but is gravely wounded in the process. Raito yells in desperation for them to free her and coincidentally, a stray bolt of lightning from an impending storm strikes the assailants. At the same time the seemingly dark cave begins to glows and a strange force pulls the two of them inside. When the two regain consciousness, they find themselves in a world different from theirs. They learn that this world is under attack by terrorist group known as the Yang Faction and every 100 years, a group of heroes are summoned to defeat them. Now if Raito ever wants to go home, he needs to stop the Yang Factiom and its leader to put an end to the long waged war with them and the villagers with the power of Yin.