Origin: Spirits of the Past (2006)
After Earth's forests take over the planet and attack humanity a few survivors are rebuilding civilisation, subject to the forest's approval. A young boy exploring ancient ruins awakens a girl who has been sleeping in stasis since the time of the catastrophe.
The premise is interesting and this might have worked as a series or a 90 hour JRPG, but as a 90 minute film there's so little depth given to the characters that none of the events have any weight, and it's impossible to care about the outcome.
Great theme tune though.