- Main article: Friends
The result of Sandstar making contact with organic matter, Friends (フレンズ) take on the form of human girls, but with features and outfits that closely resemble their original appearance. Friends also demonstrate both abilities and limitations reflective of their former selves. Like humans, they are able to speak and have a high capacity for learning and retaining information, although this varies from Friend to Friend. In addition to regular living creatures, animal remains (e.g. fossilized remains of extinct creatures or even a single lock of hair) and human ideas (e.g. mythological beasts) have been observed to turn into Friends.
Upon death, either by Celliens or unrelated accidents, Friends revert into their original form, and their lifespans rewind to the point immediately after their transformation. Subsequently, this comes at the expense of any memories gained as in their human form. It is as of yet unknown if a Friend's memories will return in the unlikely case that they came into contact with Sandstar post-reversion.
- Main article: Cellien
The result of Sandstar making contact with inorganic matter, the Cellien (セルリアン) are a mysterious race of violent and aggressive monsters which serve as the collective antagonist of the Kemono Friends universe. They are typically amorphous in appearance, although Celliens taking on more distinctive forms have been observed in the past. They are both dangerous and hostile to Friends.
A mysterious substance integral to the world of Kemono Friends media. Upon making contact with organic or inorganic matter, Sandstar (サンドスター) turns things into Friends or Celliens. It is also responsible for the drastic climate variation of the different Japari Park "areas" despite their close proximity to one another. Its name is likely a reference to hoshi no suna (星の砂), the Japanese word for "stardust" which literally reads as "sand of the stars".
In the anime, Sandstar is described as appearing from "eruptions" out of an unnamed volcano in the Kyōshū Region. This depiction is in stark contrast to that of the original game and the manga, as both stories claim it originally fell from the sky instead. Whether this detail has been retconned or will be clarified in the future is a subject of speculation.
In addition to basic Sandstar, a newly-discovered substance known as Sandstar Rō (サンドスター・ロウ) was being researched prior to the evacuation of Japari Park. Its properties are largely a mystery, although it seems that it enables certain types of Celliens to grow considerably in size and power. The meaning of the name "Rō" is as-of-yet unclear, although a comment by Tatsuki appears to indicate it means "raw".
Kemonoplasm (けものプラズム) is a mysterious substance, revealed in the third official Guidebook, which gives Friends their animalian characteristics and superhuman abilities. On normal Friends, it is found primarily in animal-exclusive extremities that regular humans lack (e.g. animal ears, wings, tails) as well as their clothing. Friends formed from extinct animals and mythological creatures have a higher concentration, with such extraordinary examples as the Four Gods being composed entirely of Kemonoplasm.
Sparkle (輝き) is a concept exclusively found in the original Kemono Friends mobile game. It refers to intangible positive qualities, such as friendship, hope, and inspiration, but also includes more practical aspects like the ability to speak. Rather than feeding on Sandstar, Celliens in the game story steal Sparkle from Friends and humans alike, which also enables them to copy their appearance.
- Main article: Japari Park
Japari Park (ジャパリパーク) is the setting of all Kemono Friends media to date. It is a massive, open zoo constructed on an island that closely resembles real life Japan. At one point, it was inhabited by humans and Friends alike, and served as a popular tourist attraction for people from all around the world. Once the Celliens invaded, however, the Park became unsuitable for humans, who have since evacuated all known regions of the island.
- Main article: Lucky Beast
The Lucky Beasts (ラッキービースト) are a group of small, armless robots tasked with maintaining Japari Park. Among their responsibilities are the production and distribution of Japari Buns, making them essential for the lifestyle of Friends. They have remained in the Park and continue to perform their duties despite the apparent departure of humanity, and are (usually) skilled guides for human visitors.
Japari Buns (Japanese: ジャパリまん Hepburn: Japariman), also known as Japari Manju (Japanese: ジャパリまんじゅう Hepburn: Japari Manjū) are the primary source of nourishment for Friends. In most cases, they are the sole food that Friends eat. Japari Buns, based on manju, are round morsels branded with Japari Park's signature "の" logo. They contain all of the nutrients necessary for Friends to live healthily, a property that applies universally to all Friends. Their exact ingredients are unknown, but at least in the Kyoshu Region, there is a field from which Lucky Beasts gather the materials to make them. Once the materials are gathered, the robots produce and then finally distribute them to the Friends of Japari Park.