There was a Korean drama where the female lead turned from 30 years old to 17 years old.

There's a novel that meets your requirements. This novel was called " A Cute Wife Descends From Heaven: Boss, Don't Be Too Bad!" The female lead was 21 years old, and the male lead was 35 years old. This was a modern romance novel, telling the story of the male protagonist being forced to marry the female protagonist and having children after marriage. The male protagonist didn't love the female protagonist at first. It wasn't until after the divorce that he realized how good the female protagonist was. This novel might suit your preferences.

Those who have watched the Korean drama " 18-years-old, 29-years-old," please come in! This Korean drama was a story about puberty and growing up. It mainly told the story of a boy named Lee Joon-Hyok's experiences and growth in high school and university. The relationship between him and the two girls was also a very important part of the story. Their emotional experiences and growth, as well as their views and plans for the future, ran through the entire story. This Korean drama was very touching. The plot was complicated, and the characters were vivid and moving.

This type of novel was often referred to as " youth pain literature " or " love fantasy novels ". The age difference between the male and female protagonists was a common plot setting. The second male lead being the son of the male lead was usually a derivative plot to express the male lead's feelings and family responsibilities for his son. This kind of novel often involved emotions, family, growth, betrayal, redemption, and other topics, which were very popular among readers.

In "Full Time Expert," Ye Xiu didn't really return to the 15-year-old storyline. Ye Xiu left home at the age of 15 and threw himself into the eSports world, becoming a top professional player. Although he experienced many challenges and growth in the story, he did not really return to his 15-year-old body or state. In the story, Ye Xiu had always maintained a mature and experienced image. His age and experience had made him a legend in the eSports world. While waiting for the anime, you can also click on the link below to read the classic original work of " Full-time Expert "!

The Korean drama " Witch " was broadcast in 2012.

I'm not sure which Korean drama you're referring to. However, if you are referring to a specific work or storyline, I can provide you with a more detailed answer.

I recommend " The Golden Age of Streaming." This urban life novel tells the story of the protagonist returning to the golden age of 16 years old and realizing his dreams step by step through his own efforts. It's a very touching and grown-up plot. I hope you will like this novel.

The Korean drama where the female lead turned out to be fat and beautiful was called Descendants of the Sun. The play was about a soldier and a doctor who met during the Second World War. The emotional entanglement between the two people and their efforts to win the war. This TV series was not only loved by the audience, but it also caused a discussion on the topic of losing weight.

For Korean dramas where the female lead was a ghost and later turned into a human, you can refer to the following example: Recently, I heard a terrible legend about a female ghost who was trapped in hell after death. She had been waiting for a chance to escape. Finally, she got a chance to become an ordinary human. So she left hell and began her new life. The plot of this TV series might be like this: the heroine's soul was trapped in hell after death, and she had been waiting for a chance to escape. But because her soul was too dark, the other souls did not want to escape with her, so she was forced to become an ordinary human. In her new life, the heroine will discover that she has superpowers such as seeing ghosts and spirits and can help other humans. She will also experience many difficulties and challenges, but she will work hard to learn how to control her abilities so that she can escape hell and return to her own world. This TV series could be very scary and exciting because the heroine might encounter many scary and scary scenes in the process of becoming a human after death. However, if the audience could adapt to this kind of plot and like this type of TV series, then this TV series might be very popular.

A few of the replies mentioned a novel with a male protagonist who was a 50-year-old uncle and a female protagonist who was in her teens, but did not provide a specific title or author. Therefore, based on the information provided, I am unable to provide an accurate answer.