At what speed must I live to see you again?

Spring 1991. Takaki and Akari meet in elementary school and continue to exchange letters even after she moves away. They make a final promise to each other to meet again. It is now 2008. They live their respective lives, paths never crossing. Enduring memories and a premonition of that promised day. Even now, their words from that day drift quietly, transcending time and distance. An ephemeral story of a promised reunion with someone precious.