Isekai Maou to Shoukan Shoujo Dorei Majutsu - Volume 9 Chapter 3 part1-6

Once upon a time, a hero had been summoned to a different world in order to defeat the demon king. After the war stretching 3 years ended the commendable hero slew the demon king. And he was forcibly deported back to earth after being dismissed.

Such bullshit!

Elves in addition to beast race, dwarfs and demon race. Even though I wanted to make a harem in the different world I saved! My dream will not come true on earth, where there is no magic at all. Thus, the hero returns on his own. Without the blunder of being extradited to earth this time, he will build a harem of his own in a different world.

“Only by enduring 2¹⁴ trials can one awaken the ancient power sleeping within the Key of the Star Prison, and become the most powerful being in the universe.”Timothy, the youngest Demon Lord in the history of his race, saw these words emerge after he touched the Key of the Star Prison, the most powerful artifact of the demon race, handed to him just before the old Demon Lord's death.According to the demon race's records, no Demon Lord had ever achieved this.However, over a span of a hundred thousand years, Timothy had easily passed 16,383 trials.Now, once again, he turned the Key of the Star Prison, and an unknown force mistakenly sent him to a brand new world, transforming him into an unknown and seemingly worthless demonic cultivator disciple.And the formidable opponent he was about to face in this world was the powerful Goddess Sylvia.When Goddess Sylvia received the challenge Timothy handed her, her cheeks flushed...“My dear Sylvia, I want you to know how deeply I love you. My heart belongs to you, now and forever.”

Sergeant Xia Yao, born into a wealthy and renown ancestry, is a playboy who has turned over a new leaf. Yuan Zong is an ex soldier from the special forces who opened a bodyguard training company after being discharged.

When Yuan Ru, Yuan Zong’s sister fell for Xia Yao’s charms, but could not break down his erected barriers, she came to Yuan Zong for assistance. Little did she know, the moment Yuan Zong saw Xia Yao, this ex-special force knew no other person would ever catch his eye.

And so begins the battle between brother and sister for the most coveted price – Xia Yao’s heart.

- Description from Novelupdates