Well, i think it can be appoached from various angles as it raises a lot of interesting issues. It's also easily forgotten that in 1959, inter-racial relationships were actually still quite controversial in many countries- there was racial segregation in the US, for instance. The film doesn't labour its points- the mind boggles trying to imagine a Hollywood film handling such topics with even half the finesse- though some might find the dialogue repetitions a bit mannered and pretentious. 

The early scenes remind a little of Woman in the Dunes- the sensual contours and textures of the bodies etc. There's a lingering sense of melancholy and irreparable damage (emotionally in Riva's case and physically in so many others from the bomb), something lost, a resignation; after such a first love other relationships can never quite have that edge or passion, yet she's intent on getting on with life, doing good, remains a decent sensitive person.

And when it comes to it, isn't memory, however flawed, all we have? At the end of our lives, it will be our memories (and regrets) that count for us. Kore-eda's After Life takes this to a precise, less subtle, conclusion.