High School DxD - Volume 19 Chapter 4.2

King Grey has unrivaled strength, wealth, and prestige in a world governed by martial ability. However, solitude lingers closely behind those with great power. Beneath the glamorous exterior of a powerful king lurks the shell of man, devoid of purpose and will. 

Reincarnated into a new world filled with magic and monsters, the king has a second chance to relive his life. Correcting the mistakes of his past will not be his only challenge, however. Underneath the peace and prosperity of the new world is an undercurrent threatening to destroy everything he has worked for, questioning his role and reason for being born again. 

A teenager named Evan Mason was reincarnated into the magical world of Harry Potter and goes to school at Hogwarts!
With only his knowledge of the future and great talent for magic, he takes the path towards the top of the magic world, only to realize that ever step he took, changed everything!

- Description from Novelupdates

To rise from defeat; to revive amidst the dissipation.

As the vast oceans turn to dust and the thunder and lightning fade away,

That strand of spiritual mist once again approaches our great world.

With the shackles that bound our world now severed—

A whole new world of mystery and wonder awaits,

As we turn the corner…

——

The Sacred Ruins is a story set in a post-apocalyptic world. A world that has recovered to a state that is roughly equal to our own world in terms of technology and culture, although its ancient history remains largely unknown. The story begins during the post-graduation trip of our protagonist, where he discovers some ancient ruins and witnesses “the great change”, an upheaval that changed everything. The changing earth not only brought about new, unexplored landscape but also sparked the evolution of all organisms. Plants and animals started gaining sentience and some humans obtained unimaginable powers. The legends, myths, and tales of old seemed to have suddenly come to life as the earth entered a new era where beasts and men formed factions, explored new lands and ultimately struggled for supremacy.

We follow the MC as he grows from being an eccentric young man into a badass expert warrior while meeting other funny characters and forming brotherly bonds. We watch as he falls into just as much hilarious situations as he does perilous ones, all the while wondering and slowly discovering the mysteries of this world. Just why was the world destroyed in the first place? Who or what had triggered this earth-shattering “change”? What profundities lie behind the process of evolution?

- Description from Novelupdates

Reborn as a sword, he lived for hundreds of years, and then he occupied the body of a 15-year-old prince.