High School DxD - Volume 7 Prologue

A wonder falling down from heaven! A boy possessed by strange blood! Gods tremble! Demons flee! A boy from the land of Dong Zhou. A pink skull as his sworn friend until death. A story of a determined warrior struggling for power. A legend that shakes the galaxy and disturbs the worlds of god, demon and man.

- Description from Novelupdates

High school student Mikoshiba Ryouma was summoned to a different world in the middle of a war. Sensing the malice from the one who summoned him (a summoner of the O’ltormea empire), he uses his martial arts to run away, killing important people of the empire during his escape. After the escape, he rescues two twin sisters from the hands of thieves. The sisters who can use magic, swear to serve him as subordinates. Thus, Ryouma begins his journey on the path of the supreme ruler.

For a million worth of contract, she became a surrogate mother.

He was the chief executive of the Empire and she was of lowly birth. With her adoptive father’s business falling into crisis, she agrees to his contract.

She gave birth to twins: the older brother is healthy, while the younger brother didn’t breathe out. Fulfilling the contract with a huge monetary sum as the reward, she disappeared from his eyes.

Six years later – he was still the cold high-profile president, but when she is accidentally imprisoned in the cage of his golden birds he pressured her harder and harder: “Woman, do not think you can escape my hands!”

The old-fashioned man: “Mu Yazhe, you’d better leave her alone, this is the child’s mother!” The man becomes frightened, questioning the reason this child’s features bears such resemblance to…

- Description from Novelupdates

An alien race invaded the Earth on June 6, 2128. At the midst of this war, many nations allied with the alien threat and the war nearly wiped out the rebelling humans of the planet. At the edge of mankind's survival, the United Nations Army launched its forces to eliminate the immediate stellar threats that loomed over Earth.

General Seeker Carlean, commander and leader of the mission, risked and gave his life to destroy the immediate stellar threat. The battle was won though Earth lay in ruins. Perhaps mankind will live to see a few years of peace before the alien threat returns to wipe out their existence.

At the immediate aftermath of the stellar battle, the fallen Seeker Carlean awakens and finds himself at aged 17, living the peaceful life he lived 16 years before he died.

So begins a new game in the battle for humanity's survival.