Klaxosaur (叫竜(きょりゅう), Kyoryuu) is a biological weapon created by the Klaxo Sapiens in DARLING in the FRANXX.

They are the central antagonists for most of the series but later joins forces with humanity to defend Earth from VIRM. They are piloted by male and female co pilot Klaxo Sapiens.


Klaxosaurs often appear as dragon-shaped or dinosaur-shaped machines. Each Klaxosaur seen to date has armor of a black coloration and glowing blue highlights. As there are four classifications of Klaxosaurs, their sizes and physical characteristics vary. They exhibit an instinctual attraction to magma energy, which they feed on.

According to Hiro, Klaxosaurs possess chemical compounds similar to the FRANXX. This is due to that the FRANXX units were designed from Klaxosaur skeletal remains. The core of the Klaxosaurs is round golden sphere and destroying it is the only way to kill a Klaxosaur.

Through Dr. Franxx‘s research, it was discovered that a Klaxosaur is the manifestation of a female Klaxo Sapien and the core of the Klaxosaur is the male Klaxo Sapien, who operates the Klaxosaur. This would become his inspiration to create the FRANXX units and the roles of the male-female pilots.


Klaxo Sapiens and VIRM war

Over sixty million years prior to the main storyline taking place, the Klaxo Sapiens were a highly intelligent and technological race living peacefully on Earth until the planet was invaded by VIRM. In exchange for sparing the Klaxo Sapiens from enduring fear and the pain of death by surrendering their souls and allow VIRM to consume them, the VIRM offered them to merge with them as a single life form. The Klaxo Sapiens refused and a massive war broke out, which lasted for several hundreds of years and costed a large number in casualties on both sides.

Although the VIRM were larger in size, they were outnumbered by the Klaxo Sapiens’ use of technology and evolution; the long period of fighting drove the Klaxo Sapiens to gradually evolve but at the cost of their reproductive organs. They built the Klaxosaurs as defense arsenals with male and female pairs; the female would merge with the klaxosaur while the male would become the core and maintain the control manuals. However, due to draining the planet’s life energy while fighting VIRM, the Klaxo Sapiens unintentionally ignited the desertification of the planet. Ultimately, VIRM was forced to retreat and the Klaxo Sapiens, having lost their civilization and sense of self due to fusing with the Klaxosaurs, went underground. The powerful Klaxosaurs were to be used in preparation for any future threats whereas the weak Klaxosaurs were turned into energy and used to restore the planet. Thousands of years would pass until the humans discovered this energy, which they referred to as Magma Energy and thought of as part of the planet’s core, and began drilling it to advance technology and their civilization.

Klaxosaurs Appear

However, a couple of VIRM escaped and, when the human race began to evolve, they disguised themselves as humans and took authority of the humans, forming the government function called APE and the leader of VIRM becoming the leader of the government and humanity, referred to as ‘Papa’. In the year 2025, Papa ordered Dr. FRANXX to develop a research project on magma energy and immortality, leading to the use of magma drilling and strengthening the economy and government.

Klaxosaur’s first appearance

Initially, the Klaxosaurs didn’t react to the drilling of magma energy until more of it was being drilled to turn humans into immortals. In the year 2037, the Klaxosaurs, whom scientists assumed were attracted to the magma energy as sources of fodder, began attacking the magma plants. The first Klaxosaur to attack a magma energy mine and make landfall near the Australian continent but it stopped after several missiles hit it, and this left the continent to declared as an exclusion zone. Dr. FRANXX named them Klaxosaurs because they were screaming reptiles. Plantations, which had initially been built as safe havens for humanity due to the planet’s increasing desertification, were turned into mobile anti-Klaxosaur fortresses and equipped with military arsenals, the remaining cities on the surface were abandoned and mankind took full refuge in the plantations.

Through research of a Klaxosaur carcass discovered in Alaska, Dr. Franxx learned Klaxosaurs contained mechanical and organic components, and they could only be killed if their cores were destroyed. He also learned they also contained XX chromosomes seen in female humans up until then. An intrigued APE council then appointed Dr. Franxx as the lead developer of their anti-Klaxosaur weapon, leading to the creation of the FRANXX units and the use of Parasites as pilots to combat against the Klaxosaurs. At some point, they became aware one humanoid Klaxosaur survived, the Klaxosaur Princess, 001.

Klaxosaurs and Humanity war

As a century of warfare passed, squads of parasites were equipped with magma energy weapons to weapon use against the Klaxosaurs and the squads were initially killed off in order to destroy the Klaxosaurs. However, this strategy was tossed in order to prolong the stockpile of parasites as the Klaxosaur attacks increased. Conflicts with Klaxosaurs became a normal expectation of parasites but the adult population gradually forgot the existence of the Klaxosaurs due to their tedium lifestyle in the plantations.

In private, APE made preparations to build Hringhorni from cores of Klaxosaurs as the ultimate weapon to annihilate the entire Klaxosaur population. Upon learning the Gran Crevasse harbored a massive weapon called Star Entity that 001 had intended to use to destroy the humans, APE sets its sight on seizing the Gran Crevasse and gaining Star Entity. However, Dr. FRANXX realized there was an issue; as a Klaxosaur weapon, it required a Klaxo Sapien to operate it, which caused the project to be delayed for a long time. Dr. FRANXX resolved this issue when he managed to obtain strands of 001’s hair following an encounter with her, and with her DNA, he created a human-Klaxosaur hybrid, Zero Two.

Due to the unexpected increase of Klaxosaur attacks, APE hastened their plan to conquer the Gran Crevasse in order to gather as many Klaxosaur cores as possible to build Hringhorni and seize Star Entity. Following this victory, two members of APE secretly met with the Klaxosaur Princess, 001, to negotiate a peaceful surrender in exchange for ending the war. She refused and killed them in retaliation for attempting to assassinate her.

Final conflict

Once the construction of Hringhorni was completed, APE sent all the parasites for the supposedly final battle against the Klaxosaurs but 001’s intervention and retake of Star Entity caused an abrupt turn of events. The two head leaders of APE, Papa and the Vice Chairman, activated a virus in Star Entity to paralyze 001 (and indirectly Hiro, who was forcibly linked with her via Strelizia to operate Star Entity) and started a countdown for a bomb, implanted in Star Entity, to detonate the entire planet. The two then revealed themselves as the leaders of VIRM before sending a horde of VIRM fleets to attack. The Klaxosaurs and VIRM began fighting, and despite the confusion, the parasites join the fight to stop VIRM once they realized VIRM were invaders. Ultimately, 001’s sacrifice to help Zero Two save Hiro from succumbing to the effects of the virus helped them defeat the VIRM fleets.

VIRM retreated to Mars’ orbit and the Klaxosaurs, then spaceships rather than monster like vehicles and accompanied by Strelizia, pursued them, igniting a galactic battle. The parasites of Squad 13 later joined the fight after discovering a Klaxosaur Mothership, which was strongly hypothesized to have been left by the Klaxosaurs as a gesture that humanity was allowed to join the fight to defend the planet. At the end, VIRM once again retreated after being defeated by Strelizia and the VIRM home planet was destroyed by a Klaxosaur Bomb, the Klaxosaurs gradually began returning to Earth, diving into the surface and becoming part of the planet, which allowed the planet to gradually prosper back into its fertile and healthy state before magma energy extracting caused its desertification. As a gesture of their commitment to the planet and newfound respect for the Klaxosaurs, the parasites vowed to never use magma energy again.


Klaxosaurs are categorized by their size. Each class is named after the discontinuities inside the Earth.

  • Conrad-class (コンラッド級): small Klaxosaurs. Even smaller than a FRANXX. Presents not much of a threat. They move quickly, rely on strength in numbers and can merge to create a bigger Klaxosaur.
    Conrad class
  • Mohorovičić-class (モホロビチッチ級): medium-sized. Can pose a serious threat to the plantations if left unattended but otherwise harmless.
    Mohorovičić class
  • Gutenberg-class (グーテンベルク級): large, intimidating and demoralizing to look at. Their siege weapons are capable of destroying plantations. Requires a joint operation to defeat.
    Gutenberg class
  • Super Lehmann-class (超レイマン級): gigantic Klaxosaurs, having at least the size of a plantation. They are to plantations what scissors are to paper and can withstand an entire plantation exploding in their face. Requires an army and a massive amount of effort to defeat.
    Super Lehmann class


Kyoryuu uses the kanji for "scream" and "dragon". It is a play on kyouryuu (恐竜), the Japanese word for dinosaur.

Klaxosaur is a portmanteau of klaxon, which is a loud electric horn, and the suffix -saur, which is derived from the ancient Greek for lizard and identifies the genera of the extinct great reptiles, the dinosaurs.


  • A Gutenberg Klaxosaur is capable of producing and recreating Conrad Klaxosaurs. According to Zero Two, the smaller Klaxosaurs are created from the Gutenberg Klaxosaur’s core.



STAMEN Hiro | Goro | Zorome | Futoshi | Mitsuru
PISTIL Zero Two | Ichigo | Miku | Kokoro | Ikuno
OTHER Naomi | Old Woman | 081 | 090 | 245 | 9'α | 9'β | 9'γ | 9'δ | 9'ε | 9'ζ | VIRM
APE Papa | Vice Chairman | Gorilla | Marmoset | Lemur | Baboon | Tarsier
Dr. FRANXX | Hachi | Nana
FRANXX Strelizia | Delphinium | Argentea | Genista | Chlorophytum | Standard | 9 Model
EPISODES 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12
13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24
CHAPTERS 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20
MUSIC KISS OF DEATH | Torikago | Manatsu no Setsuna | Beautiful World
Hitori | CÅGE | Vanquish | Escape | Darling
LOCATIONS Cerasus | Garden | Chrysanthemum | Gran Crevasse | Cosmos