It was an accidental meeting. Two strangers on a train, with nothing in common. Besides being girls of a similar age, both journeying to start new phases in their lives, and sharing the same given name, that is. Nana Komatsu, moving to be closer to her boyfriend, may be too innocent to make it on her own. Aspiring musician Nana Osaki is well-versed in scrabbling her way back up after life kicks her in the teeth. But Osaki has never experienced the warmth of family that Komatsu exudes, so while they seem as different as the symbols for Yin and Yang, they also balance each other. That's what the best of friendships do. Through good times and bad, this is the story of that friendship, and of two girls who discover that they share far more than just the same name - NANA.