At the beginning of time... in the year X8000O(X8000 OCTILLION) a Void formed... with only one Verse. And two godly beings were born to the Head of the Void. The older one hated the younger and as more Verses formed, they separated their own Verses from each other, preventing their people from entering theirs.
But... it only caused both Aizukon, the creator of Verses and Ryxun, the creator of RyonXRikujins, to be a war with each other... and those wars were called the Nightmare Grail wars.
It was only fueled when some RyonXRikujins got strong, almost wiping out all the Verses and Versyuians, but also, creating Apocalypes... so the sky would go red every apocalypse and every single human being had been used to that.
Not only that... but all happiness, joy, and peace were all erased... replacing them with a never ending cycle of trauma, misery, pain, and suffering.
And when the 11 Immortals were formed by a RyonXRikujin named Rixorikan Ruixon, it helped slowing down the apocalypses and the wars, but it only led to an 1015 year Nightmare Grail War... slowing down in X2000 and ending in 2015.
Even then... there was still no happiness. Everyone hated feeling that way.
A girl named Ixaru Vuronmen Ruixon, who was born to a RyonXRikujin as her mother, had set herself a mission to kill the founder of the RyonXRikujins before it's too late.
Reborn in the world of High School DxD, Roy is ready to conquer all with his Copy system.
But he soon discovers that his greatest challenge isn't the devils or fallen angels, but the powerful and gorgeous girls inexplicably drawn to him.
And with his ability that allows him to replicate the ability of those he touches, he will master everything....
[Do you wish to replicate this ability?]
Roy: Yup, why not?