The Guide to Conquering Earthlings - Chapter 16: 0

The “S-rank Hero Factory” that raised 1,000 S-rank heroes.

The graduates’ manufacturing machine.

The strongest support.

These are all words that refer to me. But could this actually be the world of that game?

Crossing to One Piece world, he became Roger’s younger brother.

Dreaming back to the Tang Dynasty, being an ordinary person, greedy for money, lustful, debauched and free.

- Description from novelbuddy

The story is about a a hitman, Who dies because of his own recklessness and transmigrates into a game he used to play after his retirement as a hitman.I'm not gonna spoil any further, but i might answer few of your questions.Is MC overpowered?Nope, he'll become strong over time and all battle he'll fight will be because of his effort and techniques.Is there magic and adventure?Yes! It have both magic like normal isekai with adventure and fighting with monsters and many other things. There are other important things like “Essence Stone” But let's talk about it in the chapters.There will be harem?Not really, He will be in contact with many beautiful female and males but one waifu but i haven't decided yet.All i can say is, give it a try, I'll try my best to make it worth your time.