Naruto System in One Piece - Chapter 9: Sea King

As a successful villainous BOSS, in addition to having ideas and aspirations, one must also keep in mind three points:First, grow sneakily, don't act rashly (once a villain acts rashly, they basically won't survive past three chapters).Second, you're not a good person, so be ruthless (becoming more evil will make you three times stronger, while redemption weakens you by seven times).Third, remember the two points above. The moment you forget them, your end is probably on its way.

He Lang died by his own hands for the sake of his imperial younger brother’s ambition, whom he loved. He was offered to be reborn in exchange for giving up his past romantic feelings. Reborn without the burden of his romantic feelings, he brings with him a manual to new worlds. He wholeheartedly followed the instructions of the manual to complete the tasks, not knowing that the originally slag gong was blackening…
He pleaded to his affectionate Emperor brother to release him, he pleaded to the paranoid prisoner next door, but until the end he remained baffled.
In the end, he discovered that the full name of the manual was – “Slag Shou Cultivating Manual”
Σ (っ ° ° °;) っ!

- Description from Novelupdates

Gon is the son of the duke of Hannan, but he has one problem, he has no mana. This makes him the subject of mockery among everyone in the town.It seems this is his destiny, to be ridiculed until his death but while dealing with a scroll his grandma left him, Gon gets the harem system.Name:Level:Skills:Conquered women:Potential women:The system gives him a new life and guides him to become the most powerful mage but of course this comes with enemies who Gon has to fight.This book is rated 18 because it contains lots of lemonsThere's NTR, there might be yuri.

Qin Guanglin is a regular guy living a cautiously regular life. Apart from his freelance job as an artist and his hobby of gaming, nothing has ever been out of the ordinary for him.However, when he meets a mysterious gamer girl offline, he is immediately blown away by how perfect she seems to be for him.Is it all a coincidence, or is it fate? He realizes that there is so much more to life than just staying in his own comfort zone.This is a tale of lost and found...