The main chracter is Yu Hyechan who is 29 years old.Hyechan is married to Kang Bongman who is her old classmate in high school whom she despised and hated because of his cocky attitude.But later she fell for him after being rejected by Shi Woo her crush.

This drama takes the audience back to the 1990s. The main character of the drama, Yu Hyechan, 29, reverts mentally to an 18-year-old girl after having a car accident. As she recovers her memory and the relationship with her husband, Kang Sang-yeong, she goes through many hilarious and heart-moving moments. -- KBS Global Marketing

Lee Jung-Hyun (Go Su) is accused for murdering Oh Soo-Ah's (Lee Da Hae) father. He runs away and becomes a fugitive. Later, he returns and seeks out revenge. Oh Soo-Ah who is the successor of the enterprise "First Electronic" falls in love with Lee Jung-Hyun.

Han Seung-wan (Kim Jae Won) leaves for Singapore to surprise his girlfried on her birthday, and Jung Se-jin (Eugene) is on the same flight to say farewell to her deceased "first love" who died in Singapore. When literally bumping into each other at the airport, they accidentally take each other's passports. They meet again and Seung-wan and Se-jin end up spending the day together. Se-jin knows about his girlfriend, who is two timing Seung-Wan with Min Do-Hyuk (Lee Ji Hoon). Partially to help Seung-Wan avoid from discovering the truth, Se-Jin spends the rest of her time with him. They both get drunk out of sadness of their loves, and end up sleeping together. Back in Korea, Se-jin discovers she is pregnant. She leaves to have the baby alone. A series of events happens for about a year, and Se-Jin's clueless sister ends up spilling the secret to Seung-Wan at this engagement party, showing up with Han Shin-Bi (Jung Da Bin), his daughter, without Se-Jin. Seung-wan's life is forced to face fatherhood and the anger of his two-timing girlfriend - Lee Chae-young (Han Eun Jung). Se-jin reappears as they are forced to marry by their respective families. Complicated love takes place, as Do-Hyuk starts to fall for Se-Jin, and so does Seung-Wan, though Se-Jin is more focused on her loving daughter, as something surprising happens to her. The rest of the story revolves around the family's journey in learning to take responsibility, and learning to love each other.

Gina (Hyo Ri) is a welder in a steel mill with a felony wrap behind her. With her tag as an ex-felon, she struggles to maintain any semblance of average normal life of an everyday civilian. This is a story about her trials and tribulations and how she deals with the obstacles that are thrown at her all the while maintaining a chaotic relationship with her rebellious boyfriend...

Before the marriage to fiance, a young lady Kim suddenly suffered a heart attack. She was moved to her father's hospital, but her father Dr. Kim was not able to save her. So he took her body and froze her until he could find a way to save her.

And 25 years later, in 2005, she is revided. But she cannot remember her fiance... and she falls in love with his son...

Sad Sonata is a love story about two men and one woman. The young Joon-young (Kwon Sang Woo), who was raised by his mother who sold liquor to American soldiers, met the blind Hae-in (Kim Hee Sun) and they became childhood sweethearts. Then, Hae-in immigrated to the U.S. following her aunt and her uncle[American soldier that married her aunt]. There she met Gun-woo (Yeon Jung Hoon), who was Joon-young's best friend and son of a very rich man. After she received a letter from Hwa-jung saying that Joon-young is dead, she accepted Gun-woo's love. After an operation, Hae-in was able to see again . The story picks up again when composer Joon-young, singer Hae-In, and music producer Gun-woo all meet again.

Cha Moo Hyuk (So Ji Sup) is an orphan that was abused by his adoptive family. So he ran away and learned the way of the streets, meeting all sorts of people. Because of an accident involving is ex-girlfriend, he has 3 months to live. So he goes to Korea filled with anger and hurt about his birth mother.

Then in Korea he meets someone he least expect himself to love. But how can he be able to love, hate, and revenge within the short three months of his life?