Jaehyun is actually the head of the mafia and Jeno is his son who is definitely following his path.

Jaehyun has never been married, Jeno also hasn't had a girlfriend. They are both nicknamed 'the pillar duo of life', because they have something in common. Both are handsome, cold, rich, mysterious, and have a lot of power and both are still single. Until one day they meet someone who makes them compete for him, they are familiar and absurd. But their struggle is no joke. 

Jaehyun is Jeno's adoptive father 

Jhon is a professional hitman, he always does his job neatly. He lived alone since childhood, he has gone through a very hard life which made him who he is now. Until one day he met a teenager who was abused by his parents and his life changed because of love. 

Cool but tsundere 

Mark, a lonely adult man. He is always unlucky in love stories. He is still young, only 18 years old, but because he is the only child of a rich man, his family doesn't care about him. Makes him thirsty for affection so he tries to look for it. He searched for so long that when he was 28 years old he realized that he had fallen in love with a little girl who had always accompanied him every day since he was 18 years old. He realized now that the little girl had grown up by then 

Mark is cold but he's actually kind 

Mark is a cold and indifferent person, but he is actually caring. Jeno is known to be cold and rude, but he is actually not rude. Jeno, if he was at home with Mark and his father, would be a spoiled baby, completely upside down if he was outside the house. But one day they fell in love with their own half-sister which made them compete, although in the end they gave in and instead diverged and loved their younger sibling  together (threesome) 

Jevano is a cold and indifferent person. He is the only child of a rich family whose parents are workaholics, he is often lonely and that is what causes him to become cold. But one day he met someone known as the student council president. He felt something strange about the girl, she was 1 year older than him but made him very interested. And Jevano is a very Tsundere person because he is not used to receiving or giving attention and affection 