The Dragon Emperor of Void (Male Reader X Highschool DxD)

Y/n just a normal man, until one day he die because been crashed with street light.
When he wake up, he find himself as a teenager back.
He then find a letter and it a letter from God.
it write that he should not die yet.
Because of that, the God give Y/n a power.
A power that know as 7 Deadly Forbidden Magic.
Like it name it can bring anything to an end.
His magic is Death, Destruction, Devourer, Disease, Darkness, Disaster and Dimension.
Will Y/n know who is he in this new world and how strong is he magic?