One of the reason the film is "in"famous is because it resonated with so many. Many had our first love and most never able to profess it just like how the 2 characters let the letter slip/unable to give the letter because of the external force (the wind) or the internal lack of courage that stopped us to convey our feeling.

The distance between the 2 person hearts drifts apart at the rate 5cm/s, the same speed of cherry blossom fall, slowly but surely.

I don't know a lot about western literature but in asia first love is a hot genre of romance literature. It has always been associated with melancholy, regret and bittersweetness about an unattainable yet most beautiful love.