Parasite (寄生虫 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.
All the parasites appear as normal humans. As toddlers and preadolescent children, they wear a white two-piece hospital style outfit 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 uniform with red ties (the girls’ is shaped of an X and the boys‘ is shaped of a Y), garter socks and brown shoes. When in combat, they wear special suits.
When the klaxosaurs first appeared in 2027, the human population had already been introduced to the procedure to become immortal and, after 2035, more than 70% of humanity became immortal but 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 introduces the construction of the FRANXX units but after countless failures to operate them at the cost of so many lives, it was discovered that fertile male and female pairs 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 in the Garden to be educated as pilots and, upon reaching age 14, they will be discharged and will be classified as parasites.
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. 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 given special treatment, which includes little to no supervision and hardly any punishments for disobedience, while those in the triple digits 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.
To increase their capacity and aptitude abilities, the parasites are given daily doses of yellow blood cells. For parasites whose results show some form of incompetence, an Elixirs 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, causing numerous children to succumb to its effects, with Mitsuru being a rare exception. Children who are deemed unfit to pilot are removed from the Garden and their whereabouts are kept a secret from the other children. However, it is eventually revealed the missing are kept in a hidden cryogenic room within Dr. FRANXX’s laboratory.
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. Futoshi begins showing symptoms of bulimia during Episode 16 and Zero Two develops violent mood swings in Episode 12 and 14. The parasites also develop an accelerated aging process due to the frequency of how often they pilot the FRANXX. Ikuno 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. 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. In Episode 24, this is resolved through Ikuno’s research and she develops a cure for the parasites to properly grow into adults.
Because 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’, and they are convinced they were specifically created by Papa alone.
Because they retain their reproductive organs, the parasites are biologically capable of bearing children. As they are not taught about human reproduction and childbirth, no human has conceived and carried a child to term since 2037, when APE disallowed it. When a pregnancy does occur, although not necessarily required, it is strongly recommended to terminate it. It is considered impossible for a pregnant Pistil to pilot a FRANXX because it may interfere with the paracapacity with the Stamen, and also 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 she gave 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 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. 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. If parasites possess any forbidden knowledge or engage in illegal acts, ranging from running away to getting married, they will be warranted to suffer punishments of memory indoctrination or permanently removing them from the plantation.
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.
- The terms for the pilots Stamen and Pistil are in reference to the male and female germ cells that reproduce in plants.
- All the FRANXX units and Plantations are named after plants.