Spoilers below, but mostly just about the cosmology of the Twelve Kingdoms world.
Twelve Kingdoms is an anime with the usual "modern earth kids get transported to a fantasy world" idea, except with the fantasy world being very heavily influenced by Japanese/Chinese mythology. In theory this makes it similar to Fushigi Yuugi, but based on the half dozen or so episodes of that i watched about ten years ago they certainly feel very different.
In any case, there are twelve kingdoms (duh) and each kingdom has a ruler with the mandate of Heaven. Each kingdom also has a kirin that serves the ruler. When the ruler dies the kirin goes on a quest to find a new ruler, who might be an official of the current court, or some random peasant, or anything inbetween. When they find the person they magically "know" it's the right one, and they offer them the kingdom. If they accept, they're granted immortality, plus the services of the kirin.
After that in general it follows the troperific "as the king goes, so goes the kingdom." If the chosen ruler is on the throne (metaphorically speaking) and even halfway trying to do a decent job, the weather will be mostly good, the crops and thus the peasants and thus the kingdom will prosper, and the native monsters will generally leave people alone. If the ruler leaves the kingdom or goes against the will of heaven the weather will start to suck, crops will fail, people will go hungry, and monsters will start roaming the lands. If the ruler is doing a poor enough job, their kirin will start to get sick, and if the ruler doesn't mend their ways the kirin will eventually die. If the kirin dies (either through bad-ruler-itis or some other reason) the ruler quickly follows. A new kirin will be born for that kingdom and after it matures it will find a new ruler. That process apparently takes around a decade, during which the situation in the kingdom will become progressively crappier. Also note that refusing to accept kirin's offer of rulership doesn't actually count as turning down the job, according to the gods you're still the king, you're just doing a really crappy job. Cue kirin getting sick and dying, and then you dying. So it's really on offer you can't refuse.
But on the plus side you've got a magical kirin buddy who will offer you advice (in the hopes of keeping you from going down the dark side and generally screwing things up for everyone) and the kirin has magical servants who can help keep you safe.
So why do i say they're useless?
Thing #1, which is generally well known and brought up pretty early. The kirin are good spirits in the stereotypical hippie "good is dumb" variety. Whatever you ask, they'll say that taxes should be lowered, spending should be increased, no one should be executed or even severely punished, etc. It is the common opinion of the rulers that if you actually tried to follow all of the kirin's advice things would quickly fall apart. (It's not clear if any of them has ever actually tried doing this however, or if they did what the Mandate of Heaven would decide if the kingdom was doing poorly because you followed the advice of its own messenger.) So you have to balance the pragmatism of a ruler with the compassion of the kirin.
Okay, that's a drawback, but at least one you can hopefully deal with. However in the case of the one kirin we get to see a lot of, he just generally sucks at communication in general. He does a pretty crappy job of trying to induct his new ruler. Even his non-moral advice on ruling is disjointed and useless. At one point he tries to give some advice to a new youngling kirin and he even manages to mess _that_ up.
As might be expected given the selection process, a new ruler is often dumped in the middle of a situation they know very little about. The royal court will already have vying political factions, each of which will want to preserve their own power while discrediting their rivals, and usually the situation will have been pretty unsettled for months or years prior while the kingdom was without a ruler and quite possibly suffering from natural disasters and monster attacks.
So when faced with multiple factions demanding different things, each trying to curry favor with the new ruler, the kirin's only advice seems to be "don't go along completely with one side." The kirin apparently has no insight or advice on who might actually have the best interests of the kingdom at heart. Even if they somehow feel disinclined to promote one faction over the other, they can't even seem to recommend particular individuals as being relatively trustworthy. (It's not clear if this is due to some moral stricture, political naivete, just general dumbness, or what.) The only "useful" advice anyone really seems to have given was something along the lines of "hey, don't worry too much, at least as long as you stay on the throne there won't be any more natural disasters or monster attacks." Really? Is that what we've set the bar at? Because i'm pretty sure _i_ could handle sitting on my ass and letting other people do all the work in exchange for luxury, magical powers, and immortality. Where do i sign up?
(Come to think of it, one wonders what the Heavens would do if a ruler decided to set up a constitutional monarchy and let elected leaders handle all the day to day stuff? Would they be okay as long as decent people were elected?)
And finally, at the heart of it, the kirin have just one job. Pick out the person who will receive the mandate of heaven and be a good ruler, and they can't even do that right!
A couple of the rulers have been around for about half a millennium or more and are considered especially impressive. The ones who have been around for about a hundred years are considered pretty good. But apparently just making it a few decades before going nuts isn't considered exceptionally bad. In fact one ruler notably only lasted six years. And the kicker? The kirin later admitted that when they chose that ruler they knew the ruler wasn't going to do a good job, but they didn't have any choice! It would be one thing if you accepted that Heaven didn't have _perfect_ precognition and could only tell who _could_ be a good ruler but couldn't necessarily tell if they were going to snap under pressure, so they're just betting on the averages. However if the Kirin can tell at the start that they got a bum steer then that argument kinda flies out the window. So either Heaven, and thus the Kirin, just suck at their job, or Heaven is pulling one of those crappy "this is all for the ultimate good, even if you can't understand why all this horrible stuff is happening to you" things.
I realize given that the fantasy world is a closed system if the kirin always did a good job of picking rulers the show would be seriously lacking in drama. (The Heralds of Valdemar and other series where the magical official choosers actually do a _good_ job function because there's always an outside threat.) But from an in world perspective the kirin don't seem to be much more than a fancy combination of a bodyguard and a barometer for the mental health of a ruler.
You know, i wonder if anyone has made a "You had ONE job" pic for the Twelve Kingdom Kirin yet?