Knight's & Magic - Volume 3, Chapter 28 Descent of the Fierce God (Kishin)

The ill-fated high school student Liu Yuan obtained the inheritance of the top civilization in the universe and changed his own destiny. He also used many powerful technologies in the inheritance to lead the Chinese nation to rise in the universe.

- 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.

[Successfully enhanced the Golden Snake Sword. The Winged Serpent Empress has been summoned.]

The Winged Serpent Empress said, “Master, please give the orders!”

[Successfully enhanced the Demonic Soul Armor.]

Zhou Han exclaimed, “Demon Princess, please don’t possess me!”

[Successfully enhanced the skill ‘Evil Light Ghost Queen Slash’. The Succubus Ghost Queen has been summoned.]

A Ghost Queen? With enough guts, Zhou Han could make the female ghost go on maternity leave.

Zhou Han astonishingly discovered that he awakened the only SSS rank talent in the universe: Infinite Enhancement. He was overpowered.