do you know the significance of the fish in the office at the start of the film? (and possibly why it crossfades into the moon?)
This kind of fish is called a Celestial Eye, and its most notable feature is, of course, its huge eyes, which are perpetually looking upwards. Actually, this kind of fish is basically blind, and relies on smell to move around. It also lacks a dorsal fin ; because of the very features it was bred for, it's unable to compete with others fish in a larger tank. In short, it's a species bred by humans only to be kept by themselves in smaller tanks, for decorative purpose.
The name "celestial eye" comes from a story saying these fish were bred in small pots with a tapered end. The fish originally were looking sideways like others telescope fish do, but they gradually started looking upwards in search of light.
When you think about it this way, a helpless being kept prisoner in a tank by a rich human in a position of power foreshadows the condition of the Ghost Tribe kept in a well by the Ryuga pretty well, doesn't it?
They're kept like pets in the well, and when they look upwards they see some light in...
The relation between the celestial eye and the Ghost tribe was mentioned by the staff during a talk show, so that I know for sure was their intent!
Now it's just my own thoughts and interpretation, but given how important symbols eyes, and sight, are in this movie, I can see more than just the Ghost Tribe in the celestial eye.
Despite their large eyeballs, they are unable to see, and they are kept prisoners in a weakened state by people in a position of power. To me that also fit humans such as Mizuki, unable to see the supernatural, wounded and kept prisoners by their hierarchy and, at large, the society they live in. Humans and Ghost Tribe folks aren't so different after all...
And finally, throughout the movie a lot of focus is put on Tokisada's large, shiny, round yellow eyes. He's someone who always wanted more and kept looking up, failing to ever look at the family in front of him, and at the common people beneath him. Despite his ambitions, he ends up at the bottom of the well at the end of the movie, where he can only continue to look up at the moon above.
In short: we're all the same! That's quite the foreshadow-y microcosm in the President's fishtank, haha.