5 Centimeters per Second

We all know how the story ended. Neither Takaki or Akira get to meet each other again. And when they did, they only caught glimpse of one another for the moment.

But since they are now living in Tokyo. What stopped them from seeing each other again? And when they met each other, what is going to happen? How will they interacted with one another? Or will they ran into other people instead?

Or even better, what if they somehow ran into each other again before Akira becomes engaged to her future husband?