The Breeding Deal: Brother-in-law's Forbidden Offer - Chapter 49: Twice

Xue Xi is forced to fall in love at first sight with this dangerous man on their first meeting. With death being the only other option, she makes the first move:

Her sister steal her lover

She thought it was a dream

after rolling and waking

Nightmare Reality

Her loved ones, her love, her life

They were all trapped in that big fire

burned to ashes

10 years ago, after “the Gate” that connected the real world with the monster world opened, some of the ordinary, everyday people received the power to hunt monsters within the Gate. They are known as “Hunters”. However, not all Hunters are powerful. My name is Sung Jin-Woo, an E-rank Hunter. I’m someone who has to risk his life in the lowliest of dungeons, the “World’s Weakest”. Having no skills whatsoever to display, I barely earned the required money by fighting in low-leveled dungeons… at least until I found a hidden dungeon with the hardest difficulty within the D-rank dungeons! In the end, as I was accepting death, I suddenly received a strange power, a quest log that only I could see, a secret to leveling up that only I know about! If I trained in accordance with my quests and hunted monsters, my level would rise. Changing from the weakest Hunter to the strongest S-rank Hunter!

A guy became a brother of Iron man and got the ability to extract genes from anyone. Lets see how he changed the Marvel World

- Description from Novelupdates