One Piece – Thundergod Marine - Chapter 71 Beast Tide

Falling in love with my imposter sister's fiance wasn't the plan. After finding out that she was exchanged at birth and was the real daughter of the Moore family, Eliana was expecting a turn in her life, but nothing changed except that she lived in a big house and could now eat good food. Her parents still ignored her and everything good was first given to Amber, their imposter daughter.She was twelve when she met him, when he saved her from drowning, and when she found out that he already had a betrothed. It was already known that the eldest son of the Sanders family was betrothed to the eldest daughter of the Moore family since birth. She knew this, and it was only natural that she accepted this, but the more they crossed paths, the more she wanted him and the more she wanted more for herself. Eliana was ready to do anything to achieve all her dark desires, even if it made her a villain.After all, there is a saying that goes “Villians are not born, they are made.”

Growing up parentless, Shi Yan, who was left with a large inheritance money, bore a general disinterest in life.

The only times he felt alive was when adrenaline coursed thorough his veins. He quickly found that extreme sports, bungyjumping, cave diving & skydiving, gave him the biggest kicks. The bigger the adrenaline kick, the closer he was to death, the more alive he felt.

Waking up in a pile of dead bodies in an unknown land, after a diving adventure had ended disastrously, he quickly realizes the body he now possessed was not his own.

Follow Shi Yan as he explores this new world where danger lurks around every corner, and death is only a breath away; a world in which Shi Yan could not feel any more alive.

- Description from novelupdates

I’ve had enough of being transmigrated into books.

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.