Narration? Aren't they the character's inner dialogue telling how they feel?

Of course there are several symbolisms and hints throughout the film but it is not like the male lead didn't show how he felt powerless as a child unable to profess his love or the second female character didn't realize why her feeling would never reach her crush.

Even at the last part where there was no dialogue, the song lyric beautifully captured the male lead's journey "always searching for you on the opposite platform or through window in the back alley" and his wish to have "one more time, one more chance".