My Brother Is the Devil's Enemy in His Previous Life.

The strongest demon king VS the invincible Valkyrie, a fateful duel that turned out to be close twins? ! 500 Years ago, they were mortal enemies. Now, they are brother and sister connected by blood. Long and Feiya, seemingly ordinary 15-year-old boys, are burdened with a shocking secret! The moment you step into the Holy Sword Magic Academy, the gears of destiny begin to turn! Demon ruler VS human hero, memories of past lives gradually awaken... When the former Demon King blushed and called out "Sister", when the former Valkyrie shyly called out "Brother", Wake up! Counterattack! Dominate! Will he degenerate into a demon king who is as good as a god, or will he become a hero who protects the world? What's the final outcome? Please move to the main text and stay tuned!