Thank you so much. I kept trying to see this as if it were a manga so I'd know what came next, but Ima Ichiko's level of narration is so complex I can't even come close. (For one thing, if this were hers, there'd be two other stories happening simultaneously around the living ghost one.)

No, we don't have the concept of living ghosts at all. This century we have 'out of body' experiences, but not that unconscious wandering of a person's spirit that happens without them even knowing it. The closest is maybe the ghost who appears to a loved one at the moment when the person it belongs to dies, but that's still the spirit of a dead person, just 'very newly dead' and not 'long dead' like most ghosts are.

I thought kodomono shiro was a kind of fun amusement park too, but no-- a worthy enterprise, of course, but not what it could have been.