[video=youtube;geUeWJfoLJE]http://www.youtube.com/watch?v=geUeWJfoLJE[/video]
This is kind of sad because of the story.
Humanity has destroyed itself and the planet in some kind of great war. But just before that end, a young man hid an android away in a bunker - portrayed here by Hatsune Miku - with the sole purpose of growing a single plant.
Miku wakes up and beings to follow her orders of caring for the potted plant and trying to grow it, but also remembers the one who gave her the plant and decides to go look for him because she wants to see him again. So she goes out and searches for him, completely alone in a world that is destroyed and devoid of life, but being a simple android on a mission, she doesn't actually recognize it and just sort of happily goes on her way while taking care of the plant and saying good morning to all the inanimate things she meets.
Due to the harsh and polluted environment even her android body eventually starts to break down and fall apart. Just before breaking down completely she finally finds the young man - or rather his remains, because he is already dead. When she finds him dead she feels true sadness and begins to cry, and you could maybe say at that point she becomes truly human just before she dies and achieves transcendence, or goes to heaven, or however you like to call it. The plant finally grows then and presumably renews the earth.