On Christmas Eve, Hiro Hirono's bike is stolen by a girl chasing a thief who stole her purse. He gives chase and finds her unconscious and his bike ruined. The girl, Miyako Miyamura, soon awakes and the two begin to talk. After making sure she is okay, they end up spending Christmas Eve together. Later, Hiro finds out Miyako attends the same school as him and they begin to spend more and more time together, Miyako developing affections for Hiro. Kei Shindou -- Hiro's childhood friend who has long held a crush on him -- begins to become jealous and a love triangle follows.

The anime also tells the tale of Renji Asou. One day, he meets Chihiro Shindou, the twin sister of Kei Shindou, at an abandoned train station. Though she is shy, they get along and begin meeting there everyday. However, Renji finds out that Chihiro was in a car accident years ago that gave her a disability, which makes her memory last only 13 hours. Despite this, after learning that it is Chihiro's dream to write a novel and knowing the hardships her condition will bring, Renji decides to help Chihiro fulfull her dream.