Start in DxD as Motohama: Leveling Up in Another World - Chapter 30: A new resolution, the same goal

She conspires and provokes the most powerful young master in Beijing! They sign a contract and with his every call, she has to go anywhere and do anything his bidding. When their contract ends, she smirks and said, “I’ll take the money and you can leave. We don’t owe each other anything.”

He is Young Master Ya who rules Beijing. He controls the business empire during the day, and he is the strongest king at night. He is cold and women are merely playthings to him. With his power, the women he has eyes on have never been willing to leave him, yet she is an exception. She loves money, like all the previous women, but she is never shy of showing her greed. And he never realizes that he will ever grow a heart for such a promiscuous and cheap woman…

He points a gun straight at her heart. “Die with me, or accept my love—which one do you choose?” She pouts and turns around, before she pushes an adorable child into his arms. “Here, there’s your answer.”

He was once a great Immortal, but his attempt to ascend the Nine Heavens ended in failure. Reincarnated on the Blue Star, as he opened his eyes, he found himself with an adorable daughter. And a stunningly beautiful wife?“Daddy, can you cast a spell for me?”“I could even pluck the stars from the sky for you.”

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.