The beautiful illustrations of the movie. I can't resist posting some.
The sakura petals falling when Akari first told Takaki that these petals fall at 5 cm per second, implying that is also how human lives pass.
Akari and Takaki as childhood friends, always retreating to the library and becoming good friends.
When Kanae wants to confess her feelings, she starts crying and stops as a nuclear plane zooms through the sky. Both she and Takaki look up and stare until the smoke fades.
Takaki and Akari meet again when they are adults but miss each other on the railways.