Kokirins (also 'Kirins) are a humanoid species native to Ui.

Often talked about as mere legend, Kokirins are a very rare and mystical species: it has been said that there are only six in the whole world. Of these, Nizarah, Mitori, Takaru, Posai and Kade appear in the comic's main storyline. The remaining Kokirin has not yet been named, and is known only as "Big Sister" or "Six". It is unclear whether the Mitos actually are biological siblings or have simply been brought together as a family by their unusual nature.

In appearance, Kokirins are fairly similar to humans, with a wide variety of hair colours and styles, but with downturned ears similar to those of Jitai. Kokirins also have small- to medium-sized wings on their shoulderblades; these do not enable them to fly, but may help them to balance. The wings have a tendency to expand rapidly when the Kokirin is under stress or startled. For unknown reasons, the Kokirins seen in the comic all wear small key-shaped charms around their necks, regardless of their individual tastes in accessories.

Kokirins do not visibly age in the same way as humans, although the Mito siblings do show age differences relative to one another; Posai is definitely younger (smaller, and more childish) than Mitori. They are apparently resistant to physical attacks, which seem to do only temporary damage. However, they can suffer ill health through lack of energy, a fate which frequently befalls Nizarah.

According to Nizarah, there exists some kind of medicine or serum that, when swallowed, confers Kokirin characteristics (including "near-immortality"). It can be assumed that the majority of Uians do not know anything about this.

Note: Tarin Mito and Karen Mito, who appear in the sections of the comic set on Earth, are not Kokirins.