The Shield of DxD (Tate no Yuusha no Nariagari x Highschool DxD)

The Four Cardinal Heroes were humanity's trump card in the Three Factions' war. Their legendary weapons granted them superhuman abilities and a lifespan comparable to that of a creature from mythology.

Unfortunately, as the fight dragged on, the Sword Hero and the Bow Hero died in a fight against the Fallen Angels. The Spear Hero defected to Rizevim Lucifer's side and tried to kidnap the female heir to the Lucifuge clan, Grayfia.
The Shield Hero allied with what would become Sirzech Lucifer in an effort to rescue her after Azazel pulled the Fallen faction out of the hostilities, shocked by God's self-sacrifice to stop 666.
The Shield Hero managed to rescue her, after a long and tiring fight with the Spear Hero - who unfortunately survived - and Rizevim was beaten within an inch of his life by Sirzech. Still, the original Lucifer managed to escape, plotting revenge.
The young Lucifuge heir fell in love with the Hero, but he rejected her. She didn't like that - in her eyes he should've felt blessed - so she accused him of raping her, and Sirzech believed her.
Serafall's insistence on the Shield Hero's innocence was all for naught, but then the unthinkable happened. As news of his exile reached his ears - they couldn't kill him because he was a hero - his Curse Series unlocked and the Shield of Wrath wreacked havoc only to be never heard of again.

A thousand years later, Naofumi Iwatani returns. And he's out for blood.

I do not own Tate no Yuusha no Nariagari/The Rising of the Shield Hero, nor Highschool DxD. Credits to their respective creators.