After dying in a tragic accident, two siblings are given a second chance by a mysterious Divine Arbiter - a being beyond gods, angels, and devils. Reborn into the chaotic world of High School DxD, the twins awaken as vessels of opposing forces destined to reshape the balance of Heaven and Hell. Kagehikari Tasogare, the elder twin, wields the divine power of Authority - the right to command any existence. Melan Tasogare, the younger, bears Absolute Copy - the ability to replicate any power, weapon, or Sacred Gear. Separated at birth and raised in different lands, the twins reunite sixteen years later at Kuoh Academy, a school secretly ruled by devils. But as Light and Shadow converge once more, ancient seals begin to break... and the celestial order starts to crumble. Now, observed by angels, watched by devils, and guided only by fate itself - the Twins of Twilight must choose: Will they protect the world they were reborn into... or unmake it?