Parasite (寄生虫(パラサイト) Parasaito) is a classification used to refer to children who operate giant humanoid mecha called FRANXX, which requires the pilots to retain their reproductive functions. Because all the Adults lost those abilities in exchange for immortality, the children were created for the sole purpose of piloting the FRANXX and protecting the plantations, along with the adult population, from the klaxosaurs. The male parasite is the Stamen and the female is the Pistil.


The parasites' outfit as children.

Squad 26 wearing the normal parasite uniform.

Squad 13 wearing their parasite suits.

All the parasites appear as normal humans. As toddlers and preadolescent children, they wear a white two-piece hospital style outfit and have collars with their code numbers on it around their necks while they reside in the Garden.

Upon being discharged and assigned to a plantation, they wear the standard plantation uniform, which consists of a one-piece grey and dark blue uniform with red ties (the girls’ is shaped of an X and the boys‘ is shaped of a Y), the parasite cadet badge embroidered on the left side of the uniforms, black garter socks and brown shoes. Their formal attire consists of a white beret hat with trims and the embroidery parasite cadet badge, a white and black cape coat with golden collar accents and the parasite cadet badge on the left shoulder side, and red X shaped collar.

When in combat, they wear special suits. Pistils wear a white suit with gray highlights. Stamens wear a dark grey suit and a black vest with a single highlight the same colour as their FRANXX on their right strap. Squad 13 is the only unit whose parasites wear suits that have bright highlights, as their FRANXX's highlights are of different colour.



When the klaxosaurs first appeared in 2037, the human population had already been introduced to the procedure to become immortal and, after 2035, more than 70% of humanity became immortal and the rest were expected to complete their procedures in two years but they lost their reproductive systems as a result. To prevent a population explosion, APE passed a law heavily taxing childbirth among those who remained mortal, causing a drastic decline in the birth rate.

Dr. FRANXX introduced the construction of the FRANXX units as a defense against the Klaxosaurs but after countless failures to operate them at the cost of so many lives, it was discovered that fertile male and female pairs injected with Yellow Blood Cells as a conduit for the FRANXX were necessary to pilot them. This issue was resolved through Dr. FRANXX’s cloning research and new children being born. These children spend their entire childhood raised to be educated as pilots and, once they reach their early teens, they are sent to the frontlines in male-female pairs in a ten member squad.

Initially, entire squads would be killed off in order to destroy the Klaxosaurs. However, APE developed magma energy weapons that proved effective against the Klaxosaurs and, after many sacrifices, the Garden was created as a facility to nurture the children and plantations were fitted with a quarantine zone for the children called Mistilteinn. In the Garden, the children are reared from infancy to learn the basics of FRANXX and piloting, and undergo daily aptitude tests. Upon reaching age 14, they are discharged and assigned to a plantation, where they will undergo a final aptitude test to determine if they are qualified to become parasites.

The graduation ceremony of Squad 13, with the parasites dressed in their formal attire.

Upon passing this final test, they are paired off in boy-girl pairs and participate in a graduation ceremony that is hosted by Papa and overseen by all the adult residents of the parasites’ assigned plantation. The graduation ceremony consists of the parasites dressing in their formal attire and each pair is linked by their pinky fingers with a contraband. They are then presented to Papa and the adults during the ceremony while Papa gives a speech. They will then be escorted to their FRANXX units for their startup ritual. If they successfully synchronize the units as pairs, they will officially be classified as parasites.

Upon being assigned to a plantation and promoted as a parasite, the children are assigned a meticulous routine by their caregivers that they are expected to properly follow. This consists of breakfast at 7:00, lunch at noon, dinner at 6:00, attend briefings when summoned, and interact with one another when they are not on the battlefield. All of their needs, such as food and laundry, are prepared for them in advance, but they are expected to lend a hand in chores, such as cleaning.

Main Events

When he reaches age 14, Hiro and his nine fellow squadmates are assigned to Plantation 13, although Hiro and his partner fail their capacity test. Hiro is eventually enrolled into the squad after he is found to be compatible with Zero Two, the rumored ‘Partner Killer’, and survives three rides with her. The most intense battle for the parasites of Squad 13 is the mission to protect the plantations’ ‘kissing’ in a duo with Squad 26. After initially struggling to keep up, they emerge victorious due to Strelizia arriving as back up.

During the Gran Crevasse siege, roughly 443 parasites from 200 plantations are recruited to take part in the mission despite being outnumbered against the klaxosaurs. By the end of the day, numerous plantations have been destroyed and the parasite reserves dropped to 60% due to the 265 casualties. APE arranges to gather all the surviving parasites to be taken to the Bird Nest and prepare for the supposedly final hostility against the klaxosaurs so Zero Two, as an artificial human-klaxosaur hybrid, can operate Star Entity and obliterate the klaxosaurs from existence.

However, the interference of 001 causes Papa to reveal his identity as the leader of VIRM, an alien mind-hive species that intends to absorb the souls of the humans and, with his initial plan disrupted by 001, he intends to destroy the planet with a bomb implanted within Hringhorni. Fleets of VIRM begin attacking the parasites, causing many casualties, but the parasites of Squad 13 counterattack and survive when VIRM, pushed back by Strelizia Apus, retreats. The final climax between the parasites and VIRM takes place in space, led by Hiro on behalf of humanity. Again, VIRM retreats when Strelizia evolves into True Apus. Hiro and Zero Two continue the fight for the next two years and sacrifice their lives to save the planet while the surviving parasites remain on Earth to rebuild their lives.

After the collapse of APE following Papa’s betrayal, the parasites are liberated but initially struggle to survive on their own without the guidance of the adults due their sheltered upbringing and unpreparedness to live on their own. The parasite managers take on the role of surrogate parents to guide the children and help them adjust to their newfound freedom. The caregivers take things a step further by suspending the code number system and assigns individual names to parasites, educates them with the facts of life, and grants them the choice to go as they please. As the parasites reach adulthood, they devote themselves to rebuilding the previous society destroyed by APE and their way of life undergoes a sociocultural evolution, which includes the new children receiving a proper education, the parasites using their interests to benefit their community, and the parasites becoming more family-orientated. Following the birth of Kokoro and Mitsuru’s first child, a large majority of the remaining parasites pair up through marriage and bear children, which gradually escalated the once nearly depleted human population into a heavily populated one after a thousand years pass.


The parasites are considered unique experiments as they have no parents and are biochemically conceived to become compatible pilots. From birth, the children attend educational courses that revolve around scientific and mathematical concepts that come with a FRANXX. They are ‘selected’ based on their capacity and aptitude test results and are assigned triple-digit code numbers in the Arabic numerals that denotes their capabilities. All code numbers assigned to parasites never reach past 999. The higher the parasite's aptitude, the closer the parasite's code will be to 000. Those with codes in the teens and single digits are deemed with the strongest capacities and, as favorites for their abilities, are given special treatment, which includes little to no supervision and hardly any punishments for disobedience, while those in the triple digits, who are deemed less advanced, are given less attention and receive no expectations. Hiro, who is considered a prodigy, was admired by other children from other plantations and had high expectations from the adults, making him APE's special specimen.


Doses of Yellow Blood Cells.

To increase their capacity and aptitude abilities, the parasites were given daily doses of yellow blood cells during their time in the Garden and, after their discharge, they undergo occasional testing as part of their health checkups. For parasites whose results show some form of incompetence, an Elixir Injection is offered as a choice to prevent them from being deemed unfit to pilot and removed from the Garden. While this is a powerful drug that drastically increases one’s aptitude results, it has a 15% success rate (1% in the manga), causing numerous children to succumb to its effects, with Mitsuru being the sole exception. Children who are deemed unfit to pilot are removed from the Garden and their whereabouts are kept a secret from the other children. There is a term called ‘pruning’, in which parasites who fail to meet expectations are permanently removed and discarded, which causes the parasites to suspect those who are pruned are killed, as they are never seen ever again. However, it is eventually revealed the missing are kept in a hidden cryogenic room within Dr. FRANXX’s laboratory, as the doctor, who was openly critical of APE’s ideals, found it unreasonable to destroy them.


Generally, parasites are supposed to maintain an emotionless exterior, even at a young age. Being militant dutiful, they are calm and composed, rarely exhibiting emotion and choosing their duties over anything else, even if it means putting their lives at risk. During their childhood, Hiro and Ichigo noticed how emotionless the other children became after receiving their yellow blood cell dosages. Squad 26 was noted by Hiro to be more composed than him and the rest of Squad 13 during their plantations’ friendship ceremony. Since childhood, parasites have been taught to cast their emotions aside for the sake of their duties. However, the parasites are still human and not completely able to do away with their emotions; to the contrary of APE’s perspective that emotions cloud a parasite’s judgement and hinders their priorities, it gives a boost to Squad 13’s combat skills and allows them to drastically increase their kill count because they are able to share their burdens together. Unlike most parasites, Squad 13 is shown to widely express a variety of emotions and, while they take their duties seriously, they act like normal adolescent children.

Normally, parasites have no concept of sentimentality and, other than friendly and professional comradeship, they have no notion of emotions due to their sheltered upbringing. It is uncertain if parasites are emotionless by nature or choice; they do undergo emotional indoctrination but yet they believe they must cast their emotions aside to fulfill their missions and please Papa. 090 has shown emotion many times, such as expressing anger towards Zero Two when he learned he would be forced to fight alongside her, and appearing shocked after being ordered to have his squad self-destruct, but still followed through with the order, believing it was an honor to die for Papa and the APE council. As they are raised in isolation and oblivious to life beyond the only environment they have ever known, they are naturally curious but this curiosity seems to be short-lived, as they are taught to always forget what the adults call unnecessary things, such as even their origins. Zorome shows this when he meets the Old Woman, with whom he feels a familiarity but he forgets about this after a few days due to becoming busy with his daily activities.

Patasites normally follow the rules without complaining and show great admiration towards Papa, whom they credit for acknowledging their existence the most. From their perspective, the worst case scenario is for them to fall out of Papa’s favor rather than facing death on the battlefield, which reflects their dependency on him. Parasites would prefer death if they are unable to fulfill their duties, as Hiro initially believed he served no purpose in life if he couldn’t operate a FRANXX and was willing to take the risk of riding with Zero Two as long as he could fulfill his purpose. Similarly, Kokoro became this way after her memory erasure and Mitsuru used to believe he didn’t need to live for others but only to fulfill his duties. However, some parasites gradually become skeptical of Papa’s ideals, some due to Papa’s willingness to sacrifice loyal parasites for what he calls the greater good and others when they find information that contradicts what he says. As a child, Hiro always questioned the adults about the outside world and the lack of answers only intensified his desire to learn more. Kokoro stopped believing the propaganda of APE after learning the truth of human reproduction and inspired her friends to think of the future rather than expecting to die.

Health and Lifespan

As parasites, the children experience a variety of physical and emotional effects due to the stress of piloting the FRANXX. The most common side effects are headaches and fevers (referred to as ‘child fevers’) but there are other effects. Futoshi begins showing symptoms of bulimia during Episode 16 and Zero Two develops violent mood swings in Episode 12 through 14. The parasites also develop an accelerated aging process due to the yellow blood cell injections and the frequency of how often they pilot the FRANXX. Miku starts developing some strands of gray hair in Episode 16. Ikuno also demonstrates this when her hair turns white after using Chlorophytum’s full power in Episode 21 and her health begins to weaken to the point that, within ten years, she has aged into an elderly woman despite chronologically being in her mid twenties.

Parasites are shown to possess a different physiology than the adults, who are immortal after being injected with magma energy, whereas the parasites are injected with yellow blood cells to accelerate their aptitude abilities but shorten their lifespan.

Because of their short lifespan, parasites have no anticipation on reaching adulthood by the adults, as Nana says the adults viewed the children as nothing more than tools for warfare. It is very rare for a parasite to reach adulthood, as the caregivers of parasites are revealed to be former parasites but underwent the immortality procedure after completing their duties. However, this is something only APE has the authority to allow based on how well a parasite can benefit the organization. In Episode 24, the parasite’s short lifespan is resolved through Ikuno’s research and she develops a cure for the parasites to properly grow into adults.

Intelligence and Sexuality

Parasites are shown to be highly intelligent for their age and are generally fast learners when it comes to combat by being able to gather information and use to their advantage in short amount of time. The extent of the parasites’ knowledge of the outside world is mixed; Zorome believed he would become an adult once he finished his duties and asked Squad 26 if they knew anyone who became adults, but 090 was surprised and replied Zorome didn’t know. Bcause their sole purpose in life is to pilot the FRANXX and protect the adults from the klaxosaurs, Papa and APE has banned all knowledge concerning human physiology and sexuality from the parasites. They encourage the parasites to form friendships among their squadmates to increase the authenticity of their teamwork. However, parasites are prohibited from having any relations beyond professionalism. Topics, such as romance, are considered highly taboo, as APE believes the parasites will lose interest in their priorities and become rebellious should they develop sentimental attachments. As a result, the parasites are unaware of terms such as ‘kissing’, ‘love’, and ‘sex’, all of which are antiquated actions unknown to them. They are convinced they were specifically created by Papa alone. They are aware of the meaning of pervert but attribute the term to ogling the opposite of sex.


Because they retain their reproductive organs, the parasites are biologically capable of bearing children through sexual intercourse and pregnancy. As they are not taught about human reproduction and childbirth, no human has conceived and carried a child to term since the 2030s, when APE disallowed it. When a pregnancy does occur, although not necessarily required, it is strongly recommended to terminate it. When Kokoro’s memories were forcibly altered, she was too early in her pregnancy for it to be detected and thus it was not discovered until she began experiencing morning sickness, as she was roughly a month along by then.

It is considered impossible for a pregnant Pistil to pilot a FRANXX because it may interfere with the paracapacity with the Stamen, and because the fetus lacks the yellow blood cells that are used as a conduit for the FRANXX, it may cause detrimental harm to the fetus and possibly result in a miscarriage. In Kokoro’s case, although she successfully piloted with Mitsuru in the early stage of her pregnancy, she became severely ill and had to be hospitalized before learning she was pregnant. As a result, she was banned from piloting throughout her pregnancy and received the necessary prenatal treatment, allowing her to give birth to a healthy daughter. If a parasite sires a child, protocol is that the child is to be taken away to be raised in the Garden and reared into a parasite without any contact from the parents. In Kokoro and Mitsuru’s case, they were allowed to keep their daughter, whose birth occurred after APE had collapsed and lost authority over the parasites following Papa’s betrayal.


After the parasites are discharged from the Garden, they are placed in a bygone environment that will help them develop the emotional responses needed to pilot a FRANXX. The parasites are paired in boy-girl pairs based on their capacity and aptitude results, and their obligation to function as a compatible duo is solely their responsibility. Although the pairing is arranged by their commanders, it is not permanent, and they are allowed to do what is called a ‘partner shuffle’, which is when parasites are given the choice to switch partners due to incompatibility.

The parasites not allowed any entitlements, such as individual names, nor are they allowed to exercise their own happiness without permission. They are not allowed to celebrate special occasions, such as birthdays and holidays. However, they are given presents once a year from Papa on a tradition similar to the real-life Christmas holiday. They are required to pray for Papa before meals. Upon being placed in their new environments in the upper section of the plantations, they are carefully monitored by their caregivers and are never allowed to leave unless they are reported to attend meetings for upcoming battles or undergo tests on a regular basis. They are banned from entering the city unless given special permission, though parasites part of special elite defense groups, such as the 9's, are given an S Class pass, which grants them unlimited access throughout the plantation.

The adults, who view themselves as gods, refer to the children as the “former humanity”. It is further shown that the children are bigoted by the adults for being “contaminated” with bacteria, strongly hinting that, as self-proclaimed deities, the adults look down on the artificial and mortal children. This is evident when the adults spray all objects and locations in the city that come into contact with the children, and they find it unpleasant to even speak to them.

Because they are kept in isolation and taught nothing beyond what they learn from the adults and what they experience in their plantations, they are oblivious to the outside world that doesn’t consist of warfare. They are required to follow strict rules and any violation warrants severe punishments of memory alteration or permanently removing a parasite. The threat of punishment often gives the parasites the (false) assumption that those who break the rules are killed. Minor offenses such as asking questions that contradict APE’s ideology are viewed as acts of treason but are usually punishable with a warning as long as as the questions don’t persist. Serious offenses are disobeying orders (which are punishable with potential de-promotation), possessing forbidden knowledge such as sexuality and reproduction, and parasites engaging in intimacy that surpasses professional partnerships, such as sexual intercourse. Parasites who are deemed special in the eyes of APE (such as Hiro and predominantly Zero Two) are rarely disciplined for any acts seen as violations.


Parasites appear normal humans but possesses natural piloting skills due to having endured countless tests and drills since childhood. They are biochemically created to possess significant capacity and aptitude abilities, which are enhanced by yellow blood cell injections.


  1. The terms for the pilots Stamen and Pistil are in reference to the male and female germ cells that reproduce in plants.
  2. All the FRANXX units and Plantations are named after plants.
  3. A parasite is a term used to refer to: (1) An organism that lives and feeds on or in an organism of a different species and causes harm to its host. (2) One who habitually takes advantage of the generosity of others without making any useful return or one who lives off and flatters the rich.