Eirin Yagokoro (八意 永琳 Yagokoro Eirin) is a immortal Lunarian who was involved with the founding of Lunar Capital and creation of the Hourai Elixir. She has fled the moon and now resides in Eientei selling medicine.[5] She first appeared as the Final Stage A boss and one of the main antagonists in Imperishable Night and created the Ultramarine Orb Elixir that removes the impurities in Legacy of Lunatic Kingdom. She is also the instigator behind the events of Fossilized Wonders. Personality Eirin is an enigmatic person surrounded by many mysteries and her answers regarding the mysteries about her are incoherent replies. She is generally a fairly pleasant person and is devoted to serving her ally, Kaguya, but she does not suffer fools gladly, and because of her incredibly high intelligence, she can come across as conceited, impatient and condescending at times to those not sharp enough to follow her explanations immediately. However, she also seems to lack general common sense, most likely due to her not living with humans Making any drug She can make all sorts of drug/medicines, from medicine for the ordinary cold to drugs that can manipulate dreams. As one would expect, she is not able to make medicines that would require a physically impossible process in order to produce, nor can she make the medicine if she does not have the ingredients. Although she did make the Hourai Elixir, she made it using Kaguya's ability. Besides the Hourai Elixir, she has created the Butterfly Dream Pill, which guarantees a pleasant dream, and the Ultramarine Orb Elixir, which allows the user to see the immediate future.

Natural Genius Eirin is said to be highly intelligent and considers other people to be less smart than her. Furthermore, the Yagokoro family is said to be a line of medicinal geniuses and even among them, Eirin is exceptionally intelligent. Due to this, Eirin is rarely understood by others.

Immortality It is not specified in her profile, but Eirin reveals to Yuyuko in the Netherworld Team's Good Ending of Imperishable Night that she has drunk[6] the medicine made with Kaguya's ability, in order to not die. Yuyuko's response and further narration cement that this is referring to Eirin having become immortal, from the Hourai Elixir. Freakiniess This version of Eirin is a lot more freaky and has a sadistic freajy side wich will come play when her patient presents her with her ass she'll start sexually torturing her patient by inserting things up into the patient anus while sadistically mocking the patient along with Reisen

Reisen Udongein Inaba (鈴仙・優曇華院・イナバ) is a former Moon rabbit that serves as Eirin Yagokoro's student and medicine peddler, residing in Eientei after fleeing from the Moon. She first appeared as the stage 5 boss of Imperishable Night. Since Phantasmagoria of Flower View, she has appeared as a playable character in multiple games including Legacy of Lunatic Kingdom. Personality Reisen is a meek, world-wise person[3] who is described as changing her personality completely to match her circumstances.[4] Ordinarily timid [5] and sometimes showing a scatterbrained side, she can be both carefree and crazed, and is a different person in battle. Indeed, ZUN states that her uniform is to give the impression of an inconsistent personality.[6] As she is not originally from the Earth, Reisen has never been friendly and cannot get along with humans very well[4][7]. She additionally has a lack of camaraderie with earth rabbits, who won't listen to her.[8] A comment on one of her spell cards states she may use her abilty to turn invisible to avoid contact with other people.[9]

Watatsuki no Toyohime, when commenting on Reisen's abandonment of the moon, states that that she was both self centered and cowardly, poor traits for a soldier in the Lunar Defense Corps.[10] Eiki Shiki additionally affirms this by stating Reisen's sin is that of selfishness due to abandoning her allies, something Reisen states she is "earnestly trying her best" to fix.[11] Marisa Kirisame even nominates Reisen as the most sinful of the cast of Phantasmagoria of Flower View, claiming she was "bad news" and that it was hard to get a read on her.[12]

Later on in Forbidden Scrollery, Reisen is seen peddling medicine for the Human Village, and invented a device to repel rats to assist with the Human Village's rat problem, without input or permission from her master Eirin Yagokoro. Reisen states that because her and the residents of Eientei are outsiders to Gensokyo, they should aim to be "productive members of society", as isolating themselves by aggravating others would be a bad idea.[13] As she transitioned to being an earth rabbit instead of a moon rabbit, due to having her life influenced by the events of the Earth, she felt she had an obligation to involve herself in investigating Gensokyo's incidents such as the Perfect Possession Incident[14][15], a sense of duty that Doremy Sweet calls unusual for a rabbit.[1]

Reisen is fearful of being punished[16], and at one point is so afraid of being scolded by Eirin that she resolves to sleep outside Eientei.[17] Her ears also deform and crumple from stress.[17][18] In contrast, Reisen's Dream World self is notably much more violent and belligerent, wanting only to go wild.[19] Abilities Manipulation of Wavelengths/Insanity Reisen has the ability to sense and manipulate waves of all kinds - including waves of light, sound, space, the waves that make up all things, and the waves that make up the thoughts and feelings of living creatures. Her signature use of this ability is manipulating a creature's waves to induce insanity. Reducing the wavelength of brainwaves make her target short-tempered and irrational, while increasing the wavelength leave her target apathetic and depressed. Increasing the amplitude of a wave results in an "excess" of existence, which she can use to transmit her thoughts no matter how far, while reducing the amplitude results in a "rarefaction" of existence, which she can use to silence a voice. Synchronizing waves removes interference, resulting in intangibility; offsetting the phases negates existence, which can completely hide a subject's form.[20] Reisen can also manipulate light and sound waves to deceive the senses, such as by creating hallucinations, concealing her danmaku, and tuning the vision of her enemy. She is also able to create illusions of herself that can attack the enemy, and can cast wide-area illusions that cause people to get lost.

Reisen's red eyes have a similar effect as the true full moon and can induce insanity. She can use this ability to disorient and dizzy a target, preventing them from moving straight. In addition, she is capable of releasing waves of madness from her eyes in ripples or in destructive beams.[21]

In danmaku combat, Reisen uses her wavelength abilities to render her bullets intangible, shift their position, and make them disappear completely. Her fighting style relies on using her abilities for trickery instead of raw strength, but her tricks are ineffective at making her a strong opponent.[22][23] Marisa speculates that Reisen could actually be very strong if she did not go out of her way to use her illusion abilities.[23]

Reisen is immune to the abilities of the Three Fairies of Light (seeing an invisible Sunny Milk, hearing a silent Luna Child and escaping Star Sapphire's detection) since they are based on waves. However, she seems unable to replicate Star Sapphire's abilities with her own.[24]

Moon rabbit abilities Moon rabbits can pick up "ESP waves" with their ears, forming a sort of psychic network where they can detect feelings and rumors from other moon rabbits, no matter how far they are. Reisen can still participate in this network despite the physical and spiritual distance between Gensokyo and the Moon.[16] Reisen along Eirin will join on the sadistic torture of the patient and she can use her abilities to amplify the stimulation or create false stimulation or make the patient go insane in general as she takes the same much freakier and sexual personality to her usual self