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A basic Cerulean as it appears in the 2017 Kemono Friends anime. Note the stone on the back of its head, which is just barely visible from the front.

The Cerulean (Japanese: セルリアン Hepburn: Serurian) are an aggressive, invasive species of monster which is formed by the union of Sandstar and inorganic matter. They are mainly amorphous in shape, although they come in various shapes, sizes and power levels. They are the collective antagonist of the Kemono Friends multimedia franchise. Ceruleans are a threat to Friends and humanity alike, absorbing and devouring them if given the opportunity.


Official merchandise featuring the name "Cellien".

The origin of the name "Cerulean" is not known for sure. While it's tempting to assume it refers purely to the shade of blue or cyan, Ceruleans across all Kemono Friends media in which they are featured come in many different colors.

One prevailing theory on the word is that it is a portmanteau of cell and alien, owing to their typically amorphous, cell-like appearance and otherworldly, invasive character. This is supported by official Kemono Friends merchandise, which includes an iPhone case that romanizes the word as "Cellien".


Although it is understood that they are born from Sandstar coming into contact with inorganic matter, the details of Ceruleans' origins aren't fully understood. They were discovered at approximately the same time as the Friends themselves and much of what is known about them comes from research conducted on specimens captured early in their developmental stages.

Ceruleans were present early in Japari Park's history, but were considered a only minor threat to the staff, Friends and park facilities. Early reports equate them to "vermin", but (correctly) make the assessment that larger specimens, which were at that point rarely seen, could pose a much more significant danger.


A Cerulean's typical appearance compared to its actual composition. Depicted specimen is Alexandrium catenella.

Ceruleans come in all shapes and sizes. Although those featured in the game and anime were at least half the size of a Friend (and often much larger), research reports included in the second guidebook confirm that Ceruleans early in their development are much smaller, ranging from the size of large insects to microscopic specimens. The fullest extent to which a Cerulean can grow, if there even is such a limit, is unknown.

Early research reports by human experts in Japari Park described the bodies of Ceruleans as "translucent like hard jelly beans", "rainbow-colored and beautiful" and "possessing a texture which is somehow both rigid and wiggly". Their body temperatures cannot be felt upon touch. The properties of the "eye" of a Cerulean are compared to that of a nucleus, and research notes reveal that destroying it causes the entire body to collapse and vanish. Despite their often round and amorphous, algae-like appearance, they are in reality comprised of an assembly of blocks.

All Ceruleans featured in the anime have been groundbound, however species capable of levitation and flight appeared in the original game. A great range of strength between species can be observed in all Kemono Friends media in which they appear; there are weak Ceruleans as well as very formidable ones possessing advanced capabilities. Reports included in the second guidebook make note of a tendency for large specimens to possess more complex movement patterns than their smaller counterparts, suggesting that size is a determining factor in the range of a Cerulean's capabilities.

Types of Ceruleans which appeared in the original Kemono Friends mobile game.

In the original mobile game, Ceruleans explode into block-like fragments after receiving sufficient damage, and a triumphant "パカァーン!" (Pakaan!) is displayed on the screen. In the anime, a Cerulean is usually defeated by striking an exposed stone somewhere on its body, at which point it bursts into blocks as usual. It can be assumed that the reason they burst into these cube-shaped fragments is because of the "LEGO block"-esque composition of their bodies.


Unlike Friends, whose behavior largely resembles that of humans despite their animalian heritage, Ceruleans are almost exclusively depicted as mindless and aggressive monsters. They are a major threat to other organisms, and their presence has been the cause of at least two evacuations of Japari Park. Ceruleans feed off of Sandstar as well as organisms formed by it, which is why they mercilessly attack Friends, but they are evidently a threat to humans as well. Upon locating a target, they will attack it mercilessly, a process which only ends with the prey escaping or through the death of the Cerulean itself. Friends that are devoured will lose their human form and revert to their original, animalian body thereafter. They survive the process with their lives, but at the expense of all their human-like capabilities, as well as the memories gained as a Friend.

Ceruleans possess some degree of shapeshifting ability, taking on the forms of other organisms, including but not limited to algae. It is for this reason that the Ceruleans are able to hide the cube-like composition of their bodies. They are also capable of such feats as transforming their bodies for use in battle and combining together in a "computer-like circuitry" to carry out more complex activities.

In the original Kemono Friends game, they are responsible for stealing Sparkle from Friends and humans alike, and can use it to transform into more advanced forms. Cerval and the Cerulean Queen are two such examples.

Special Variants

There are a great many types of Ceruleans encountered across Kemono Friends media. Many of them are fairly generic and have no special properties beyond their combat strength, however a few unique examples exist and warrant direct mention.


Cerval addresses the Cerulean Queen during the climax of the game story.
Main article: Cerval

A Cerulean resembling Serval with several irregular properties, who is in possession of Serval's unique Sparkle. Unlike regular members of her species, she is capable of speech and emotion, developing a friendship with her Friend counterpart over the course of the original game's story. At the end of the game, she joins the player party as a full-fledged Friend.

Cerulean Queen

Also appearing in the game, the Cerulean Queen once possessed the sparkle of Kako, enabling it to grow incredibly powerful. It is the antagonist of the game's plot, and was defeated by the player's party at the story's conclusion. Upon defeat, it reverted into its true form: an unremarkable, basic Cerulean, which immediately scurried away.

The second guidebook reveals that the gender of the Cerulan Queen, despite its name and basic appearance, is unknown. Its armor is comprised of other Ceruleans.

The giant Cerulean faced in the final episodes of the Kemono Friends anime.

Giant Cerulean

An immensely powerful class of black Cerulean first seen in Episode 11 of the anime. It has no formal name, but it is understood that it is able to absorb a special type of Sandstar from the Sandstar Mountain, which it lives in close proximity to. By absorbing the special Sandstar, known as Sandstar Raw, it can regenerate its body when wounded and grow larger and stronger. It was evidently because of this Cerulean that the Kyoshu Region needed to be evacuated and abandoned, as Mirai's final logs reveal. Although she and the other Friends in the area were unable to defeat it, the results of her investigation detailed in her last recordings prove indispensable to Kaban in her final battle against this formidable monster.

The logs, substantiated by interactions during the finale of the anime, indicate that the giant Cerulean is attracted to fire (ranging from tiny flames to the sun) and will follow it blindly regardless of its surroundings. It is also extremely vulnerable to water, and upon contact with it, the affected area petrifies into volcanic rock. This is seen when Friends incapacitate one of its legs in their effort to free Kaban, as well as during the giant Cerulean's final moments, where it plunges into the ocean and hardens into a small island. Whether this weakness to water extends to all Ceruleans is unknown, although in the Nexon game, the water-based attacks of certain Friends (such as Blue Whale) do not appear to have any special effect.

Concept art of the Dark Hunters.

Generation 2 Ceruleans/"Dark Hunters"

Another class of black Cerulean featured solely in the original game's after-story. Whether they are connected to or separate from the giant Cerulean in the previous section is unknown. These Ceruleans, tentatively known as "Dark Hunters" (DH), possess frightening capabilities and a much more complex range of behavior than their standard counterparts. The report on DHs in the second guidebook hypothesizes that they are a natural evolution of regular Ceruleans, but notes that Professor Kako thinks otherwise.


Kemono Friends (2017 Anime)
Major Characters KabanServalLuckyMiraiRaccoonFennec FoxEmperor PenguinGentoo PenguinHumboldt PenguinRoyal PenguinSouthern Rockhopper Penguin
Minor Characters African Wild DogArabian OryxAsian Small-Clawed OtterAurochsAxis DeerBlack-Tailed Prairie DogBrown BearCampo FlickerCrested IbisCrested PorcupineEurasian Eagle-OwlEzo Red FoxFossaGiant ArmadilloGolden Snub-Nosed MonkeyGray WolfHippopotamusJaguarJapanese Black BearLionMargayMooseNorth American BeaverNorthern White-Faced OwlPanther ChameleonReticulated GiraffeSand CatShoebillSilver FoxSuri AlpacaTsuchinokoWhite Rhinoceros
Cameos AardwolfAtlantic PuffinAustralian DevilAxolotlBearded SealBergman's BearBlack JaguarBlack LeopardCapybaraCougarCrunchyroll-HimeEzo Brown BearFrilled LizardGiant PandaGolden TigerIndian ElephantIndian PeafowlJinmengyoKing CobraKodiak BearLeopardMalayan TapirMaltese TigerOcelotOkapiPlains ZebraPolar BearRed KangarooRed PandaRock HyraxScarlet IbisSika DeerSouthern TamanduaTasmanian DevilThomson's Gazelle
Savanna AreaJungle AreaMountainDesert AreaLake ShorePlainsJapari LibraryPPP LiveSnowy Mountains AreaLodgeCeruleanAmusement ParkBus-Like
CeruleanFriendJapari BunJapari BusLucky BeastPenguins Performance ProjectSandstar