Eirin Yagokoro


Brain of the Moon (Eternal)

The usual outfit of Eirin from the world of eternal night. The contrast between red and blue gives her an aura of competence.

Brain of the Moon (Eternal)
Voice Lines
Temperament: Tsukigasa

Tsukigasa (a Touhou LW original) refers to an atmospheric optical phenomenon in which a halo appears around the moon. This is an apt temperament for Eirin, who created a fake full moon and sealed the surface. Eirin is endowed with Fire Phase, as she sought change and not constancy, and Moon Essence, as a sage of the moon.

Ability: Capable of making any drug. Natural genius.

The ability of Eirin Yagokoro from the world of eternal night (a Touhou LW original). It is essentially the same as our version of Eirin's ability. She can create any medicine with her amazing skill if she has the right ingredients. She also has an outstanding mind that is not limited to just the field of pharmacy. She is one of the Sages of the Moon, and her intelligence is so great that she was even consulted for advice by Tsukuyomi, who is said to be the founder of the Lunar Capital. It seems that the Eirin of this world is more than capable of prolonging the Eternal Night Incident... While Eirin serves Kaguya, she is also Kaguya's teacher and kind of like her mother or guardian as well. Their relationship is more complicated than a simple partnership. Although Kaguya's abilities are complex, unknown, and expected to be very powerful, it is thought that Eirin has utilized her abilities to create the Hourai Elixir, an immortality medicine. This means that Eirin is at least familiar with Kaguya's abilities and may even completely understand them. It is theorized that Eirin did not just receive Kaguya's help by giving her specific instructions but also performed the extraordinary feat of turning the concept of Kaguya's abilities into an ingredient for medicine. This hypothesis is possible only because Eirin possesses a genius brain and ultimate pharmaceutical skills. And if this hypothesis holds, Eirin should also be able to fully comprehend the abilities of her other students, the Watatsuki sisters, and maybe even materialize their abilities into ingredients for medicine. Unlike our world's Eirin, the Eirin of this world has not managed to come to the conclusion that Gensokyo's barrier alone can sufficiently shut out the moon emissaries. This has directly led to the incident being prolonged, meaning that Eirin's secret technique, which created a sealed chamber by swapping the full moon with a fake moon, was never broken. The eternal night that was created to combat this spell must have also been extended somehow. Perhaps this Eirin's method of creating a sealed chamber was different from what happened in our world. It is unclear how the Eirin of our world performed her spell, but it is possible that this Eirin performed it by manifesting someone else's ability. Thus, it can be assumed that the Eirin of this world also caused the incident to test her spell. The test must have been successful, meaning there was no need to worry about an invasion from the moon emissaries. And even if something unexpected occurred, Eirin could prevent any attack by copying the enemies' abilities as ingredients for medicine, which she could then apply to her spell. Since this would block intrusion more reliably than Gensokyo's barrier, Eirin no longer had any reason to undo her seal on the surface...


Moon Shot

The Spread Shot of Eirin Yagokoro from the world of eternal night (a Touhou LW original). She summons destructive innovations in this attack. Although Eirin is a genius, she is not the kind of sage that just sits at home and doesn't act. This attack is the ultimate battle of wits that challenges the opponent to think empirically and logically. This challenge by a true sage also tests whether the opponent has the courage to take decisive action, like how Eirin fearlessly saved Kaguya. Shooting at the moon is a fool's act, but a sage can actually hit the moon. She may be an example of someone who has completely mastered the art of battles of bullets.

  • Waxing Gibbous Shot
  • Eve of the Full Moon Shot
  • Full Moon Shot
  • Night After the Full Moon Shot
  • Waning Gibbous Shot
  • Last Quarter Shot
Lunar Thinking

The Focus Shot of Eirin Yagokoro from the world of eternal night (a Touhou LW original). She manifests educational guidance in bullet form. This attack is essentially Eirin's instructional whip as a teacher of the moon. It is not exactly known what kind of mental process lunar thinking is, but Reisen Undongein Inaba seems to have mastered it. Although youkai are very different from humans, Lunarians are actually considered to be the most alien beings from humans. The more distant a lifeform is from humans, the more difficult it is for humans to guess their ecology and thoughts. This is because humans can only come up with ideas based on what they themselves have experienced.

  • Lunar Thinking: Introduction
  • Lunar Thinking: Basics
  • Lunar Thinking: Application
  • Lunar Thinking: Practice
  • Lunar Thinking: Advanced
  • Lunar Thinking: Secret Technique
Forbidden Medicine: Hourai Elixir

A Spell Card of Eirin Yagokoro from the world of eternal night. This attack imitates the forbidden elixir. The fates of Eirin and Kaguya were drastically changed when Eirin created the Hourai Elixir with Kaguya's ability. Whoever consumes the elixir will become a person of Hourai, a being with true immortality that can never perish. In return, they will become impure and can no longer live on the moon. The name ''Hourai Elixir'' could mean a ''medicine from Hourai,'' but it is also possible that Eirin just named it after Kaguya. If Kaguya could make a medicine of immortality, all the authorities on Earth would surely fight over her. Still, Kaguya would probably reject everyone and continue to be an anti-Cinderella... But the real question is, how does this medicine taste? Is it bitter?

  • Hourai's Light
  • Hourai's Elixir
  • Hourai's Illumination
  • Hourai's Mysterious Medicine
  • Hourai's Vivid Light
  • Hourai's New Medicine
Medicine Sign: Great Galaxy in a Jar

A Spell Card of Eirin Yagokoro from the world of eternal night. She creates a starry sky within a jar that has no inside or outside. This sealed area without boundaries is Eirin's secret technique that completely separates the moon and the Earth forever. Her pupil and the greater youkai, who rely on boundaries to travel between the moon and the Earth, will probably struggle to use their abilities if Eirin uses this attack. It is similar to a black hole, without a doubt.

  • Jar's Star
  • Jar's Sun
  • Jar's Moon
  • Jar's Constellation
  • Jar's Fixed Star
  • Jar's Satellite
Heaven Spider's Butterfly-Capturing Web - False Moon

The Last Word of Eirin Yagokoro from the world of eternal night (a Touhou LW original). This attack differs from the original because it was merged with her spell, which creates a sealed room. She uses multiple surveillance networks to observe the moon and the Earth. They are said to be set up somewhere between the moon and the Earth, somewhere that can never be identified since the boundary between them has been erased. This place could be in the Dream World or another dimension. The only thing that is certain is that this is the Net of Eternal Wisdom that Eirin created to protect the princess and Eientei for eternity.

  • Fake Moon's Light
  • Ground Monitoring Bit
  • Heaven Net
  • Spider Net
  • Moon Monitoring Bit
  • Butterfly Net


Skill: Drachenblut

A compound medicine that can be used as both poison and medicine. The ingredients are dragon's blood, tree resin, cinnabar, and Calamus Draco.

Skill: Sura With Soda

A poisonous drink that induces a state of severe intoxication. Ingredients are rice flour, syrup, and madhuca flowers.

Skill: Five Minerals Powder

This is the generic form of an elixir from China that is said to sharpen the senses. Ingredients are stalactite, red halloysite, sulfur, white quartz, and purple quartz.

Passive: Hourai Body
Passive: Too Much Fun Is Poison
Passive: Royal Guard