Takaki Toono and Akari Shinohara are close childhood friends that harbor feelings for one another. However, due to certain circumstances, the distance between them begins to widen. Having promised to keep in touch with one another, they are challenged by distance and time, but their unfaltering love remains. Even so, the strong emotions they feel may not last forever.

Byousoku 5 Centimeter is a drama that revolves around the difficulties of being in a long-distance relationship. Despite the time they spent together being nothing but a distant memory, Toono and Shinohara refuse to give up on seeing each other again, thus unknowingly hurting those around them.