Toaru Majutsu no Index: New Testament - Volume 1, Prologue: The People Who Became the Protagonists by Some Kind of Mistake. War?

“I'll take this child.” Sold to the Wudang Sect's outer martial arts training hall for three silver coins at a young age, Kwak Yeon dreams of mastering supreme martial arts. But can he overcome the needle-sized gateway barely permitted to trainee instructors and rise to become a disciple of the main sect? “A true gentleman cannot stand idle in the face of injustice!” Thus begins Kwak Yeon's unyielding journey through the martial world, following the ruthless principle of “Kill Buddha, Kill Ancestors”—destroying all obstacles in his path!

The status of a wizard is transcendent in all continents and in the universal plane.

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. 

When the cosmic tyrant Frieza detonated Planet Vegeta, home of the Saiyan race, a twist of fate sent a lone infant—placed in an escape pod by his mother—hurtling through the void toward an unknown destiny. The pod's trajectory led him to a desolate world: Titan, a planet ravaged by catastrophe and long stripped of life.Beneath the shadowed skies of this barren realm, the watchful eyes of Thanos, the self-appointed director of the universe's population balance, beheld an unexpected sight—a child, the sole survivor of Titan’s forgotten civilization... a child with a tail swaying behind him.“A survivor of Titan... From this day forth, you shall be my son.”