Kaizhai (開齋) Air Nomads are ethnic Air Nomads who conceal their origins, their airbending, and often their religion in response to the Air Nomad Genocide. Descending from the survivors of the Air Nomad Genocide, they can be found scattered throughout the Earth Kingdom and, to some extent, also in the Northern Water Tribe, continuing to hide from the Fire Nation. Kaizhai communities vary in the level of secrecy and degree of true or pretended assimilation they have undergone.

Unsurprisingly given their lack of safe contact with each other, Kaizhai groups are very diverse. Some continue to practice the Air Nomad religion openly in the Earth Kingdom or Northern Water Tribe, which is not particularly distinctive insofar as, particularly in the Northern and Western Earth Kingdom, there are significant populations of people who are of non-Air-Nation descent but who are believers in the Air Nomad religion as taught to them by missionaries. In this context, Kaizhai Air Nomads simply adopt the outward dress and peculiarities of their local coreligionists. With this practice involving little moral distress, these people have often completely integrated into their new settled communities and have often deliberately chosen to intermarry with those of different ethnicities but shared religious beliefs. Knowledge of the secret Air Nation heritage of some community members is kept from outsiders, but within it, trusted people may know. As the Fire Nation has sometimes persecuted non-Air-Nation practitioners of the Air Nomad religion, though, their position is considered relatively precarious, and they have usually fled in advance of the Fire Nation invasion when their communities are in its way. Since the term "Kaizhai" implies some relaxation of religious practices, this first group is arguably not really Kaizhai at all, and instead just refer to themselves internally as having "settled."

Whereas the "settler" crypto-Air-Nomads have abandoned nomadism but not their religion, the next group of Kaizhai typically refer to themselves as having "gone to ground." They retain a nomadic lifestyle, but have joined non-airbending nomad groups, typically non-settled Waterbending groups (sometimes even disguising their airbending as waterbending at a distance), or the nomadic peoples of the Western Earth Kingdom. (Some of these groups, such as the Abka and Yonggan, have had historical connections with the Air Nation and religious sympathies toward the Air Nomad religion.) The great majority of "gone to ground" Kaizhai have modified their outward religious practice, though some have joined with steppe Yonggan and Abka tribes who converted to the Air Nomad religion centuries ago during the Great Ri patronage of the Northern Air Temple. Many "gone to ground" Kaizhai no longer practice vegetarianism, though they may attempt to eat less meat than their non-crypto-air-nomad peers, fast, obtain vegetarian food where available, etc. The degree of assimilation pressure is high as most of these nomadic societies are high-context and expect their members to share in their traditional religion, diet, and practices (which might include violence against criminals, for example.) For most of these Kaizhai Air Nomads, their original ethnic identity is a closely guarded secret, even within their adopted nomad bands. As of 99 AG, the Fire Nation does not seem to have caught on to the existence of this group.

A somewhat atypical group of Kaizhai, who might be called "Kaizhai Air Nationals," are descendants of the settled people of the Air Nation, i.e. non-nomads living in the territory of the Air Nation. Such settled people may or may not have been of similar genetic background to the majority of Air Nomads; for example, substantial populations of ethnic Fire Nation and Earth Kingdom people came to live in the Air Nation as a consequence of the Great Treasure Donation. Also, there were settled cultures which arose out of the same geographical and genetic matrix as the majority of Air Nomads. The Fire Nation included anyone in the Air Nation as intended victims of its genocide, with a narrow exception for those who had no documented ethnic Air Nomad or airbending ancestors for four generations - and could convince the invaders of that. Many of these people, unsure of their ability to prove their ancestry or just not wanting to live under Fire Nation rule, fled to the Earth Kingdom.

Finally, there are Air Nomads who live among non-Air-Nation settled people and do not openly practice the Air Nomad religion. They may continue to do so in secret, or may disguise their practices as more local religious traditions (not necessarily hard to do, given the outsize influence of Air Nomad religious thought on other world religions.) These are the prototypical Kaizhai, and have usually modified their religious and cultural practices to better conceal themselves. They may be endogamous or exogamous, and may or may not teach airbending in secret. Because of the degree of religious compromise usually involved, most of these people descend from more-or-less devout secular Air Nomads rather than clergy, and so they tend not to have had high degrees of bending skill to begin with. Many Kaizhai in this group - who may not even be aware of the term Kaizhai - settled alone or in family groups, and are totally unconnected with, and indeed unware of, other survivors of the genocide.

By midcentury AG, almost all surviving Air Nomads were thought to be Kaizhai. Prior to that, there were out-of-the-way settlements and monasteries that survived the initial attacks; the Fire Nation found and destroyed most of these as well within a few years. Over the years, reports of these hide-outs being discovered and destroyed by the Fire Nation (often by elite or mercenary raiders striking deep within the Earth Kingdom) have dwindled, and none of good reliability have been heard in decades. Of course, it's possible to some extent that "all the Air Nomads who were bad at hiding are dead," and some truly secret refuge remains, but even the Fire Nation appears to have given up on finding such a place. They instead focus the limited effort they expend on eliminating Air Nomads on finding Kaizhai in their occupied lands, and they now barely investigate rumors of secret Air Nomad monasteries and the like.