[Warning: Spoilers Ahead]

The secret entangled between Na In Woo and Park Min Young has been unveiled in the latest episode.

In the tvN drama 'Marry My Husband,' Yoo Ji Hyuk (Played by Na In Woo) revealed the blue heart to Kang Ji Won (played by Park Min Young). 

At the end of episode 6, there was a surprise turn of events when Yoo Ji Hyuk recognized the BTS songs such as "Dynamite" and "Spring Day," which were revealed in the future. Then, in the latest episode, Episode 7, it was revealed that both Kang Ji Won and Yoo Ji Hyuk had returned to the past after experiencing death. 

In the episode's opening, Kang Ji Won disclosed her unusual plans for her husband, Park Min Hwan, and her best friend, Jung Soo Min, to get married. Later in the episode, Yoo Ji Hyuk revealed a poignant detail from his experience in the future – he had attended Kang Ji Won's funeral. He recounted, "It was sad. A lot of people had regrets," sharing his reflections on the somber emotions he had experienced during that time.

It was revealed that Yoo Ji Hyuk had assisted Kang Ji Won right after returning to the past so that he could ensure that she could live a new life. Yoo Ji Hyuk regretted not seizing the chance when it was given to him and decided to remain next to Kang Ji Won and protect her with his life.

At the end of episode 7, Yoo Ji Hyuk reveals to Kang Ji Won the blue heart mark on his collarbone and asks Ji Won, "Didn't you say your dad drew blue hearts on your allowance?" and adds, "Your dad's allowance." He continues to show his intentions to assist Kang Ji Won in her revenge and says, "So you can use me all you want. It's okay."

But Kang Ji Won responds, "I don't have to spend it, right? I just want to talk with it. And I want my allowance to be happy. Is there anything you want to do in your second life?" and tells him, "I want to be happy. I want to be happy on my own. with my strength. I'm going to be happy."