Shizuku Tsukishima is a star student attaining high grades at the final level of compulsory education despite her reluctance to follow everyone else into high school. One day as she reads through her library books she notices that they have all been taken out by the same person before her - the mysterious "Seiji Amasawa".
Later, as she travels on a train she notices a lone cat that appears to be travelling by itself. It gets off at the same stop as her and she decides to follow it. After it leads her to an old antiques shop run by Mr. Nishi, she enters on a path of self discovery and finds out who Seiji is.
Cutting to the chase, Whisper of the Heart is a Japanese animé - which is not to everyone's taste. It is however rated for children, so it is not necessarily marketed as a film for adults. That said though, it is a beautiful tale told in an equally charming artwork.
Despite having 16-year-old protagonists, Whisper of the Heart covers issues that would be more suited to an adult. In fact, when releasing the film to the American audience, Disney had serious enough reservations to change the dialogue during the dub to dumb down the adult feelings between the characters. Interestingly, it did seem a little bizarre for people of that age to be declaring their undying love for each other.
Of course, these uncomfortable feelings arrive simply because the film is aimed more towards children. As part of growing up, these emotions are raw and quickly shift from happiness to sadness and back again on a sensation rollercoaster. As such, the film would be far easier for someone at a similar age to Shizuku to empathise with.
If you're a big burly man I would recommend watching it with a loved one in order to keep your image up, but you'll probably still enjoy it regardless. It is an animé that deserves to break through into the mainstream market.