Yukari Yakumo is an often seen and referenced youkai from Touhou who is the Youkai of Boundaries, residing within the border of Gensokyo. While she is powerful enough to do things on her own, she is also one of the laziest residents of Gensokyo, preferring to have others do it for her because she thinks it's more fun. Yukari has two Shikigamis, Chen, the Nekomata Shikigami, and Ran, the Kitsune Shikigami, and has the ability to teleport through and control boundaries. Yukari's relationship with Reimu is complicated, but she tends to either help Reimu or pester her, and can be a hero or a villain depending on her whims and whatever the situation demands.
Over a thousand years ago, Yukari organized an army of youkai and led them in an invasion of the Moon. The youkai were subsequently routed by the Lunarians, who possessed superior technology and magic, and forced to retreat to Earth. Since that time, no youkai have attempted to expand their territory beyond Gensokyo. While some speculate that Yukari organized the invasion out of selfish hunger for territory and power, others believe she did it to teach the youkai a lesson about starting wars of conquest; namely, that it was a bad idea.
About a thousand years ago, Yukari met and became friends with a human girl named Yuyuko. After Yuyuko died, Yukari continued to be friends with Yuyuko's ghost, although Yuyuko gradually forgot who she had been and why she had died. When Yuyuko requested that Yukari use her power to weaken the border between the Netherworld and Gensokyo, Yukari obliged. She knew Yuyuko's plan to make the Saigyou Ayakashi bloom could never succeed, but was too busy sleeping to say or do anything about it, or to put the border back to normal after everything was finished, which put her on a collision course with the heroines.
Yukari is known for being a very youkai-like youkai who sleeps all day and lives for the enjoyment of life. Though she rarely leaves her house, she's well-connected and is acquainted with most of the most powerful youkai (such as Suika and Yuyuko) as well as anyone having anything to do with the Hakurei border or outside world (Reimu Hakurei and Rinnosuke). She's possibly the most powerful youkai in Gensokyo, and has a tendency to toy with her opponents rather than use her full power from the start. If anyone is suited for the role of "mastermind", it's Yukari; she often has a great deal of insight and understanding about whatever happens in Gensokyo, and possesses considerable intellectual prowess as well. Though she seems flaky and unreliable most of the time, when the safety or security of Gensokyo is at stake, she won't hesitate to get involved, even if it means using others to do the work for her. For example, in Scarlet Weather Rhapsody, she treats Tenshi Hinanawi with much hostility after finding out the plot of the Heavens.
Yukari is a Youkai with the appearance of a young woman with long blonde hair who carries a parasol as well as a paper fan. In Touhou 7, she wears a deep purple short-sleeved dress with white elbow gloves and a pink mob cap and has purple eyes, and rides on a red boundary, and her parasol has pink laces. In Touhou 8, she wears a pink mob cap like in Touhou 7, as well as a pink and purple long-sleeved dress, carries a pink parasol, and has dark golden eyes. Her main palette in Touhou 7.5 and 10.5 has the same appearance as in Touhou 8, except her hair has been coiled up into her white mob cap.
Yukari is known for being a very youkai-like youkai who sleeps all day and lives for the enjoyment of life. Though she rarely leaves her house, she's well-connected and is acquainted with most of the most powerful youkai as well as anyone having anything to do with the Hakurei Border or the outside world. She's possibly one of the most powerful youkai in Gensokyo and has a tendency to toy with her opponents rather than use her full power from the start. If anyone is suited for the role of "mastermind", it's Yukari, and she often has a great deal of insight and understanding about whatever happens in Gensokyo, and possesses considerable intellectual prowess, as well. Though she seems flaky and unreliable most of the time, when the safety or security of Gensokyo is at stake, she won't hesitate to get involved, even if it means using others to do the work for her. For example, in Scarlet Weather Rhapsody, she treats Tenshi Hinanawi with much hostility after finding out the plot of the Heavens. She could easily be either a villain or a heroine, depending on her whims.
According to Perfect Memento in Strict Sense, she seems to rarely attack humans. She excels at mathematics and is experienced due to her long life.
Yukari deals with problems by manipulating others to act to resolve things for her. She seems to rarely act directly except in particularly egregious situations. In all cases, she rarely lets anyone know what her true aims or goals are, and sometimes these goals are extremely abstract. Yukari has a well-deserved reputation of being fickle, whimsical, and lying often, and thus many characters in Gensokyo dislike her. For whatever reason, Yukari takes it all in stride and does not seriously deny any of those comments. She seems to actively try to keep her more obviously-altruistic actions a secret, such as her donations to the Hakurei Shrine in Strange and Bright Nature Deity. She possibly cultivates this image to ensure that people continue to fear her as a youkai, as this is what her true goal for a particularly complex gambit is revealed to be at the end of Cage in Lunatic Runagate.
- Ran Yakumo (Shikigami)
- Chen (Ran's shikigami)
- Reimu Hakurei (Friend)
- Yuyuko Saigyouji (Friend)
- Suika Ibuki (Friend)
- Rinnosuke Morichika (Friend)
- A silhouette of Yukari occupies the front of Perfect Cherry Blossom's jewel case.
- For some reason, Yukari's appearance in spell card 222 in Imperishable Night is different from other characters. Instead of using the new image in Imperishable Night, a modified image from Perfect Cherry Blossom is used (she has blue ribbons instead). What is more strange is that the background used in the spellcard, which is also from Perfect Cherry Blossom, uses Yukari's original cut-in image with red ribbons. Yukari's sprite in Shoot the Bullet also sports blue ribbons
- Although not explicitly stated, Yukari is commonly considered one of the most powerful youkai in Gensokyo, although a few other youkai like Suika Ibuki and Yuugi Hoshiguma have been considered to be around her level. However, she might still lose spellcard battles to humans or youkai. Yukari does refer to Eiki Shiki and Watatsuki no Toyohime as being stronger than she is, and tries to avoid direct confrontations with them.
- Regardless of her power, Yukari appears to be the most well-informed being in Gensokyo of any kind, and usually achieves her goals through manipulating events rather than direct combat.
- She is the only Phantasm boss in the series. Her status as "8th boss", however, is matched by Komachi Onozuka and exceeded by Eiki Shiki (Phantasmagoria of Flower View having 9 stages); Reimu can also become a stage 8 or 9 boss in Phantasmagoria of Flower View (if playing as Komachi or Eiki respectively) or a stage 8 boss in Scarlet Weather Rhapsody (if playing as Tenshi).
- There is a train service in Japan called やくも ("Yakumo").
- In Scarlet Weather Rhapsody, one of Yukari's spell card spawns a train to mow her opponent down. The graphic of the train is based on an actual existing train 長野電鉄木島線3500系 (Nagano Electric Railway Kijima line 3500 series), a train used to run in Nagano: ZUN's homeland.
- The Gensokyo Record in Perfect Cherry Blossom's prologue says that the original Gensokyo boundary (presumably the first "boundary between inside and outside" mentioned in Yukari's Perfect Memento in Strict Sense article) was created by priests, but ZUN said in his e-mails that the Gensokyo Record is not reliable, and that only the long lived youkai knows the true history of Gensokyo. The Akyuu firmly believes Yukari was involved and Curiosities of Lotus Asia Chapter 26's prologue states that Yukari being its actual creator is an ongoing rumor.
- Ran tells Remilia Scarlet in Silent Sinner in Blue chapter 3 that Yukari invaded the moon to procure its secret of power to improve the youkai quality of life. This is probably the official reason Yukari gave all youkai for the war, as otherwise, Remilia could confirm Ran Yakumo was lying just by asking around. However, privately, in Cage in Lunatic Runagate Chapter 5, Yukari reveals to Ran that she knew it was impossible for the beings of Earth to ever win a direct confrontation against the Lunarians. It is never stated when Yukari made this realization, so it is possible she knew this even before the first Genso-Lunar War. In addition, The last chapter of Cage in Lunatic Runagate has the line, "While it was Yukari who led the invasion that had convincingly failed more than one thousand years ago,". The word "convincingly" could imply it was staged. If this was the case, then presumably the outcome where youkai decided to stop expanding beyond Gensokyo was Yukari's true intent.
- It is not stated who sealed the Saigyou Ayakashi. It was someone who held Yuyuko Saigyouji very dear, judging by the record ("My wish... is that she will never again reincarnate, and never again suffer pain..."). Yuyuko's profile describes the hypothetical breaking of the seal as "breaching the boundary". The boundary sealing the Saigyou Ayakashi is apparently the boundary between life and death, as this is what the BGM that plays during the Saigyou Ayakashi's reflowering represents. Boundary of Life and Death is one of Yukari's spell cards. This possibly implies it was Yukari who sealed the Saigyou Ayakashi. Yukari's profile reveals she knew all along that Yuyuko's body was sealing it, and gives a clear motive, as the tree was killing too many humans. As another possible indication, The Grimoire of Marisa brings up the butterfly dream regarding Yuyuko's spell card during the Saigyou Ayakashi's reflowering, which is a theme associated with Yukari.
- Regarding the vampire incident in Perfect Memento in Strict Sense, it is not stated who were the powerful youkai that defeated the vampire, who signed the contract with the vampire, or who was the one who wrote the original draft of the Spell Card rules that came afterwards (as it was also written on youkai contract paper, Hieda no Akyuu feels it wasn't the Shrine Maiden). However, the colophon at the end reveals that Yukari wrote a work called "Vampire Pact". This possibly implies her involvement in at least one of these things (if not all three).
- Yukari edited Perfect Memento in Strict Sense and was one of its major sources, according to Memorizable Gensokyo, yet did not confirm her involvement in the above events. One common thread regarding them seems to be that they primarily benefited humans, not youkai (besides possibly the vampire contract, but it went so overboard towards protecting humans that youkai complained to the shrine maiden).