Base-Breaking Character: Either Shoukei and Suzu are the best examples of Character Development in the whole series, alongside Youko, or they're so whiny (Suzu) and/or entitled (Shoukei) that their change came in too late for them to actually become sympathetic.
Ensemble Darkhorse: Shushou doesn't appear all that much but she is very well-loved in the fandom for her snark, badassery, intelligence and hyper-competence all while being a little girl. She also gets bonus points for trying to set the still not wiser Shoukei in her place.
Les Yay: Rangyoku seemed pretty interested in Youko disguised as "Youshi", even after she learned that "he" is a "she"...
Risai has quite a bit in the novels, with fellow Gyousou-loyal judge Kaei.
Love it or Hate it: There aren't too many people who are neutral about this series, due mainly to Youko's whiny attitude for the first five episodes (and first third or so of the novel). Regarding the anime, the general rule given to newcomers seems to be... watch the first seven episodes; if you don't hate the series at that point, you're going to like the rest of it.
Narm: The evil Queen of Hou is named Kaka. It sounds exactly like a (very childish) Spanish word for... poop.
Strawman Has a Point: Shoukou has a point when he points out that the system where kingdoms' rulers are decided by a kirin is silly, especially since the kirin's choices are NOT infallible and most rulers eventually wind up hurting their kingdom.
JustifiedAppeal to Force: Without a kirin's direct demonstration of the monarch's receiving the Mandate Of Heaven (or without the latter's literal Contractual Immortality), victories such as Youko's re-subordination of her own illegally-dispatched royal army, and subsequent 'major alterations' to her previously corrupt court would have been all but impossible due to human nature, especially as regards politics. Bottom line: if she hadn't been made a God-Empress, possessing the fealty of even supernatural beings, Youko wouldn't have been able to escape being a Puppet Queen. Strawman conveniently forgot to mention that failure to live up to the divine responsibility necessarily results in fatal judgment, or that a strong-willed, good, absolute monarch can cleanse a land of corruption/evil approximately infinity times faster than democracy. Eventually, Youko herself explains to her court, and even Keiki, what she has decided the real problem is: an entire culture encouraging terror at the prospect of challenging, but especially speaking out against, wrongdoing by superiors. Kei doesn't get better until she forces it to do so.
While the judgement of Heaven may be certain and eventually fatal, it is anything but swift. The King of Hou killed 600,000 of his own people, a fifth of the population, and the only reason he didn't kill more was that his people declined to wait for the shitsudou to carry him off and... expedited the process. To make things worse, the judgement of Heaven initially manifests as bad harvests, disease, natural disasters and the like. In other words, the punishment for a ruler losing the Way falls on the people rather than on the ruler, and that's on top of whatever the ruler is doing that made him a bad king to begin with. In all, it's hard not to wonder what the King of Heaven was thinking when he set up this system. And of course, unlike purely human systems of government, which can be fixed, there's not a thing anyone can do to correct the flaws in this one.
Shoukei throwing stones at the Wa executioners, just like the son of the old peasant woman. Quite the turning point in her Character Development.
Asano's death in Shoukei's arms, and when Youko, Shoukei, and Suzu mourn together for him. Especially when you consider that Asano really did die for nothing, and he knew it.
What Measure Is a Non-Badass?: Face it, fandom. If Youko had not been "a coward", "a pushover", and a "zero whiner and unsympathetic lead", she would have not grown into the physically/mentally strong yet still kind and sensitive Action Girl we love. It's repulsive to see people whine and complain about how Youko starts out as a total moron, refusing to see that she was raised in a very exigent household (specially thanks to her very demanding father) as well as subjected to lots of pressure, so it's very understandable to see her stumble and be terrified at first. Dissing and badmouthing the flawed and insecure Youko from the beginning is NOT the best way to praise how she develops through the series.
Similarly, a good part of the fandom accuses Suzu of being a wangsty and whiny Scrappy — without taking in consideration that this is a product of her extremly harsh life in the Twelve Kingdoms, including 100 years of abuse coming from her mistress. It's a miracle that Suzu isn't even whinier, and not to mention her share of Character Development is about her stopping to be whiny and self-pitying, and learning that she can take control of her own life.