How will we escape the fate of mankind? If you want to see an action flick, you'll have to pass on this one. But if what you wanted to see is a contemplative movie about homoerotic love and violence, then this is what you've been waiting for.
The movie is set in a prison with the atmosphere of a Buddhist temple. Light, shadow, heat and flesh are at every corner. The film is quite enigmatic, but even if you don't understand, the story is busy enough to keep your attention.
I think that the film tries to convey some Buddhist reflexions about life. The prison is perhaps a symbolism for the false appearances of the world, and the pyramid and spaceship a symbol of enlightenment or escape from the world. There is also a questioning about causality. Kazuka's death blurs the line between murder and suicide. Who's will was it that caused his death? One might be tempted to say his own, but then the movie says that it was the rainbow. Isn't this an example of interdependent origination? To take a phrase from the Wikipedia definition: "This is the understanding that any phenomenon 'exists' only because of the 'existence' of other phenomena in an incredibly complex web of cause and effect covering time past, time present and time future." This might also explain the movie's (japanese) title: "A love of 4.6 billion years", which corresponds to the age of the earth. Anyway, perhaps other commenters will make better sense out of this, but it is undeniable that this is a contemplative movie that might make you think (if you're willing to).
As for negatives, the movie is short and somewhat unfocused.