Bestow Whole Favour on My Lovely Wife - Chapter 45 - Then ask yourself

The world that nurtured the civilization which reached the pinnacle of magic was on the verge of destruction.
The last survivor transmigrated to the past, when the magic civilization started growing, as countless mages were still fumbling their ways through the thorny paths of magic knowledge.
He, who came from the end of the magic era, aim to reach the pinnacle of magic.

- Description from Novelupdates

“They said the world would fall without me.”“They said I was the strongest.”“Then they buried me with honors... and a blade behind my back.”Remiel St. Clair, humanity’s strongest exalt, prince of a once glorious empire, was betrayed and buried.Nine centuries later, he awakens in the body of Lucien Callastre, the second prince of a kingdom descended from his own treacherous bloodline.Stripped of powers, but not of pride, he must rebuild his lost strength and rise to power yet again to fend off the ever-growing threats of the spirits.The maw is growing.The spirits are returning.But so is he.And this time, the Exalted Prince is not dying quietly.

The world was at the brink of collapse. Humanity’s desperate battle against the Harbingers, monstrous alien invaders from another world, had raged for years, leaving cities in ruin and hope at an all-time low.Amid the chaos, Noah Eclipse, an eighteen year old with no past and no purpose, struggled to survive each day.Noah being a first-generation talent, with a common, unremarkable ability that never stood a chance against the Harbingers' overwhelming might, had spent years labeled a loser, while fighting to keep his head above water in a world that seemed to have forgotten him.But as fate would have it, everything changed one day when he was fighting for his life and at the verge of dying.[Congratulations, you have awakened an SSS RANKED Talent : Void Summoning][Congratulations you have unlocked one item : Eclipse blade!!][Congratulations : You have unlocked a new skill; Void Blink]He was reborn, and for the first time, he was no longer weak nor helpless.With all the creatures and the power of the void in his palms, he would bring an end to the apocalypse!

agreed. He thought they might just talk, have a few drinks, and that nothing significant would happen. However, she invited him to a hotel, and they spent the night together.The next morning, she told him it was just a one-night stand and that they would probably never meet again. She said goodbye and left. Ronan also decided to treat it like that.The next day, at his college's hosting club, Ronan was given the responsibility of hosting that year's annual function, where they had invited a singer.When Ronan looked up at the singer, he was shocked—it was the same woman he had spent the night with. After checking her history and social media, he formed an impression of her. Every picture she posted was in revealing clothes, bikinis, or almost nude outfits.He concluded that she was just a promiscuous woman, likely driven by lust, and that she had probably chosen to spend the night with him simply because she found him handsome.Understanding this, Ronan decided to focus on his work. That morning, she had made it clear that it was just a one-night stand and nothing more. He would treat it exactly that way and carry out his responsibilities.Protagonist has System---No NTRIt's Harem, with many girls but The Singer is Main Heroine.