There once was a boy and a girl. They lived their entire childhood as neighbors, so they were bound to become friends. They did, and their parents became close as well. The boy and girl grew up side by side as best friends, sharing their meals, throwing surprise birthday parties, lending a shoulder to cry on, putting everything out of their way to help the other, and so much more. It looked so much more than friendship. All the other kids teased and joked about how they'll get married in the future, how they're perfect for each other. Even their parents were convinced that they would get married.

They never married each other.

No, they were only friends all their lives. Best friends, and only that.

In college, the girl and boy grew into a woman and man. The women met a different, but wonderful man. The man met a brilliant woman, who is also different from his best friend. The two friends met and dated these different people, and, eventually, they married them. Today, the woman and her husband have two children. A girl named Kim Ah Young (17) and a boy named Kim Joon Young (11). The man and his wife have two children as well. Two boys named Park Bo Gum (17) and Park Bo Kyung (10). The two families lived in an apartment complex as neighbors, and history repeated itself. Kim Ah Young and Park Bo Gum grew up together, even as they were in the womb. Now they are high school students with middle schoolers for younger brothers.

Will history continue to repeat itself? Or will something change?