Avatar - Conquering the Elements - Chapter 9. Lost

In the vast Marvel universe, where superpower was still slowly growing in its infancy, several peerless superheroes tried to find their path in The Marvel Universe. A young adult named Ron from modern Earth unwittingly stumbles into such a world and begins his journey with an unknown power. This is a magnificent yet unknown true marvel world! This is the story of a normal young adult and his adventures!

- Description from Novelupdates

Marry him for a contract, but it is love that supports them to live together.

In order to raise medical expenses for the seriously ill father, she had to sign a contract with a strange man, she would be his wife, and he was responsible for paying for the treatment of her father.

Life after marriage is very ordinary. He is the CEO of the company. He is busy working every day and occasionally has a look at her, but he is full of disgust. However, she fell in love with him little by little, and she was very sad when facing his indifference. Neither of them knew how to resolve the misunderstanding between them.

After experiencing the death of her father and an unexpected pregnancy, they finally opened their hearts, and sincerely, began a happy life.

Seven years ago, she freely and easily abandoned ￥100 and ran away, carrying her unborn son with her. Seven years later, she returned with the lady killer’s genius son, never expecting that her darling son would sell her out to MBS International. Unexpectedly, her immediate superior was the Mr. ￥100 from seven years ago!

An average man is reincarnated in the world of DxD! How do you survive in a world of battle-hungry monsters? With a cheat skill, of course! Devour the competition, becoming stronger with every fight! From the depths of the Familiar Forest, the Beast King will rise. (Harem, Gamer!SI)