Cosmic-Level Demon God - Chapter 3 - 1: Aspirational Class, Summer Job_

In her past life, she lived with guilt all her life, and even when she finally saw her enemies get their retribution, it could not heal the deep scars in her heart.Rebirth finally gave her the chance to turn everything around.Armed with her inherited space and a wealth of materials, watch how she compensates for her regrets and harvests a fulfilling and happy life in that era of material scarcity...But why was the icy, indifferent man, whom she had a vague liking for in her past life, still so devilishly clever, so ruthlessly exposing her biggest secret so quickly?The new book “The Fierce and Charming Wife's Rebirth” was released on May 31.The new book “The Space of the Shepherd's Delicate Wife's Rebirth” has been uploaded.

Violet skies, a world undergoing massive changes, a deficient moon, interlinking voids…
When the world experienced a cataclysmic event,the majority of living things ceased to exist. Although humanity survived by hiding in the last safe zones, humans had to face mutated dire beasts and colossal source beasts that could break through the space barrier and enter the earth at any second.
Luo Yunyang, a young man who grew up in those calamitous times, obtained an attribute regulator and set out to walk the path of supremacy!

- Description from novelupdates

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.