Song Ju and Jeong Seo who have lost a father and a mother respectively spend their childhood together like real siblings. Song Ju is there for Jeong Seo whenever she feels lonely and has a hard time, and Jeong Seo also relies a lot on Song Ju. However, after Jeong Seo's father gets married to Tae Mi Ra, Mi Ra and her daughter Yu Ri keep harassing Jeong Seo out of jealousy. Tae Hwa, Yu Ri's rough and wild older brother, has a crush on Jeong Seo who is pure and kind unlike him.
Kim Min Gyu has wealth and success, but lives an isolated life due to his allergy of people. He then meets and falls in love with a girl who is pretending to be a robot for her ex-boyfriend, a genius robots professor.
Jin-ho Jeon is a very stylish young man with the perfect looks. Jin-ho has also some faults which include being self-centered and obsession with cleanliness. Jin-ho Jeon then comes across Gae-in Park, a woman hurt by love and is now looking for a gay roommate/friend. Jin-ho wanting to live with the woman, then pretends to be a gay male.
Nam Shin is a son from a family who runs a large company. After an unexpected accident, he falls into a coma. His mother Oh Ro-Ra is an authority on brain science and artificial intelligence. She creates an android named Nam Shin III which looks like just like her son Nam Shin. The android pretends to be Nam Shin and he has a bodyguard So-Bong.
As a child, Park Hoon and his dad were kidnapped and taken to North Korea. He grew up there, learning to be a doctor just like his father. When Park Hoon escapes back to South Korea and begins work at a prestigious hospital, he makes it his goal to earn enough money to go back to North Korea to rescue his true love. He'll do anything to find her, but then he meets and falls for a mysterious woman who looks exactly like her.
Orphaned Jang-geum becomes the first female physician in the Joseon Dynasty and her determination is tested when people around her start showing their true faces.
A woman puts everything on the line to achieve her goal of being able to move into a luxury penthouse in the Gangnam District. In the process, she gradually finds herself turning into a monster.