Genesis Code: The Genetic Awakening - Chapter 7: First Quest

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.

One day, Luo Jian woke up from his sleep and found himself in a locked chamber where the door and window were all sealed. A note with a few lines written on it was tacked to the wall: “Escape from this room within an hour, otherwise, you will die.”

There is a sequel called Reincarnation Night (轮回之夜) that takes place in the same universe but has different main characters

- Description from Novelupdates

Kanda Kyoichi transmigrated to Konoha and became a temporary instructor at the Ninja Academy. Fortunately, he awakened the Mentor System.By teaching others, he could earn rewards.Thus began Kyoichi’s career as a “teacher” in the ninja world.Shisui: “Sensei’s unique interpretation of the Will of Fire has given the Uchiha Clan a true sense of direction!”Asuma: “The essence of the jade lies in protecting the people, with the advanced leading the way for the less experienced. Only then can Konoha become stronger!”Kakashi: “He’s my life mentor. He transformed Konoha!”...Years later, in the memoirs of Kyoichi, now the Hokage, he wrote:“I honestly just wanted to be a life mentor!”

Choices. Crossroads. Opportunities.Plunged into a broken world ruled by the strong, Damien must decide how his newfound life will proceed. Navigating through conflicts and alliances, his journey intertwines with the fates of powerful figures and kingdoms, challenging the very fabric of the hellish world.Set against the backdrop of the legendary One Piece universe, this tale reimagines familiar characters and lore, weaving a narrative that explores themes of power, redemption, and the indomitable spirit of adventure. Damien's quest is not just for treasure or glory but a deeper pursuit of a truth that could change the course of history.As the tides of the Grand Line shift and churn, Damien confronts the harsh realities of the pirate world, facing challenges that test his limits and forge his legacy. In this saga of the high seas, only the bold dare to dream, and only the strong survive. Will Damien rise to become a legend among pirates, or will the unforgiving waters claim yet another soul? The journey to discover 'One Piece' is as perilous as it is wondrous, and for Damien, every choice and battle is a step closer to his ultimate destiny.Join him as he goes against all odds in the world of Pirates, Marines, and Revolutionaries, sailing on the Path to Power!