Okami Wa Nemuranai - Chapter 3.15

For decades, the brave warriors of the Northern Army fought to keep the world safe from the evil Silent Night. But when the fourth-generation leader, Jin Kwan-Ho is accused of colluding with the enemy, he is forced to disband the sect and commit suicide to protect his son, Jin Mu-Won. With no family and allies left, Mu-Won leads a dreary life under close surveillance… until a surprise attack from the Silent Night gives him a chance to escape to the mountains.

There, the young warrior trains to master the fighting techniques of his predecessors, before the mysterious disappearance of a loved one brings him back to the mainland. Follow Jin Mu-Won as he embarks on a journey to avenge his father’s death and take down the villains who threaten to plunge the world into darkness!

As childhood sweethearts, they were made to engage under the manipulations of their families. It involved having to to live in the same room and sleep together.

One night, she is accidentally made drunk, and in his delirium, he kisses her only to realize he enjoys it. From time to time, he would sneak a kiss on her, but his “crime” is eventually discovered in an accident. After being accused by her, he says with a smile, “You are my wife, why can’t I kiss you?”

The two people’s daily routine is full of bickering and mutual discrediting of each other.

Although he claims to disparage, he actually cares intensely about her. He feels crazily jealous when she is close to other men, to the point of tying her to his side, so that she becomes exclusively his.

- Description from web

Arakawa Kouki is reincarnated to a Japan with a different history than the Japan he knows with the memories of his previous life still intact. Kouki was discouraged, “Aren’t reincarnation stories supposed to be at some fantasy world filled with swords, magic and elves?!”

There are a total of seven sins, and a revelation is made to a young man named Alex that he is destined to become a demon lord, more especially a demon lord of sin called LUST.

It's not like he can change that and because he always knew something about himself was different—not in a physical sense, well, maybe a little—and not in a mental sense—but rather because he is thrown into a demonic war that compels him to accept his new reality.

He was only aware of a difference in himself. Relating to him and the ladies who are drawn to him... Well, it was more or less like he was a magnet in front of all the girls, and all the girls were drawn to him like a metal.