Miko is characterized as being "surprisingly casual", and frequently jokes around. Though she's a fully immortal hermit, she still tends to get involved in secular affairs because of her origins as a ruler. During combat, however, she displays no sign of weakness and seems to completely see through her opponents. As a hermit, she isn't concerned about teaching her techniques to the many that want to become her disciples, and simply uses them as servants and couriers. She's cooperative and friendly towards humans in general, though. Due to her ability however, she may not listen to people's conversation.

Miko is a charismatic individual who has the ability to easily win people's hearts. She speaks in a very confident manner, even when talking about uncertain and future subjects, and thus people tend to believe her. Her nature was described as of a "very politician-like politician". In Symposium of Post-Mysticism, Miko expressed interest in acting as an "administrator" for the Human Village to prevent collapse of its society, but stepped back when she was told that it was not necessary.

In speech, first person, she uses the word "watashi" (私, "I") in first person and "kimi" (君, "you") in second. It also seems like she uses "anata" (貴方 "you") for those who acknowledge her true power. Since she's a saint, it would be appropriate for her to be polite in general. She apologised for being impolite to Reimu Hakurei when fighting her and invited Reimu to her home in Senkai

As literally stated, Prince Shoutoku – according to legend – was so smart that he could understand ten people questioning him at once, and reply to each of them with perfect answers. This is pointed out by her name, "Toyosatomimi". Because of this ability Miko's ears are extremely sensitive, leading her to wear earmuffs.

Miko, who is from a high noble family, has from a young age heard many grumbles from government officials around her. Although one would think that nobody is usually able to understand such government officials, she understood all of it, and was able to give precise instructions to them. The aforementioned thus became a rumour that spread throughout society, and thus she gained tremendous popularity as a saint.

In addition to this ability, which she acquired through the faith she had received as Prince Shoutoku while in her long slumber, Miko gained the ability to hear other people's desires. By listening to the other's "ten desires" simultaneously, she gains insight into the personality, motives, and identities of whose desires she listens to, and thus is able to know everything about the other person; although, originally, such an act wasn't possible before. This power is referenced by the game's title Ten Desires. However, this ability is not all-powerful, since she has trouble analysing those who inherently lack one or more of the ten desires. In the case of Youmu Konpaku, who – as an irregularity – lacks two desires; this is due to being a half-phantom who lacks desire of neither life nor death, so Miko is unable to completely understand her. She's also unable to read Koishi Komeiji at all.

Miko is trained in Taoist magic, seeming to favor spells themed around light and swords. She has displayed a number of abilities typically associated with hermits, including shukuchi movement (with the aid of a cape), pyrokinesis, shooting beams of light and evoking swords as melee attack or projectiles. During Reisen's scenario in Urban Legend in Limbo, she was also able to break Kaguya Houraisan's spell that made the corridor inside Eientei endless. According to Miko, since Kaguya's spell connected minuscule gaps in space-time, she neutralized it by using a hermit art that absorbs space.

Miko has displayed the ability to attract and absorb desires from her surroundings (usually in the form of vulgar spirits) to increase her power. In Hopeless Masquerade this takes the form of a secondary popularity meter, increasing or reducing her stats depending on the crowd's opinion of her. During the firework festival in Grimoire of Usami, she transmutes the enthusiasm of the audience directly into concentrated light for her spell card "My Way is Truly That of Heaven!". It is unclear whether this ability is related to her status as a saint and/or god, or simply an extension of her ability to hear desires. Miko's skill Wishful Soul of Desire likely transforms the desires into a projectile ball.

Miko's a hermit living in Senkai. Though she apparently has disciples, she doesn't teach them her ways, but rather treats them as servants. Her main goal is to achieve immortality, and then eventually become a celestial. She has shown interest in becoming a leader to human society as seen in Symposium of Post-mysticism, coincidentally the surge of a leader in the Human Village is seen as the biggest threat to balance in Gensokyo for youkai society as mentioned by Aya in Forbidden Scrollery and possibly referring to Miko.

The sword that Miko holds is assumed to be Shichi-sei ken (七星剣) lit. Seven-Star Sword, a Chinese-made sword originally owned by her namesake which was influenced by Taoism. It's one of two swords Prince Shotoku was most famous for.

Her primary weapon is a shaku, which is also commonly associated with Prince Shoutoku.

Toyosatomimi no Miko is the true identity of Prince Shoutoku, a politician and advocate of Buddhism in the sixth century. According to her profile, she was born in a stable, and was revered as a genius from a very young age, able to offer advice to people much older than her. She was all out in displaying her talents and abilities, but because of her genius, she was dissatisfied. She considered: "the earth hasn't changed from the age of the gods, and the seas are still filled to the brim. Why must humans be forced to accept death?" Upon this consideration however, she eventually turned against her natural fate as a human – to eventually die.

She was then approached by Seiga Kaku, a hermit who heard of the rumour of Miko and taught her the ways of Taoism. She was delighted at hearing that it was a religion that was a realisation of true immortality, but she also conveyed to Seiga that Taoism wasn't a religion suited for ruling a country.

They then hatched a plan: because Taoism isn't sufficient for calming the problems of an entire people, she took on the appearance of advocating for Buddhism instead, which preached peace. Seiga proposed the remedy that she would have the outwards appearance of having faith in Buddhism, a religion that has strict rules against the killing of any kind of life. Accepting the condition that in this way, the country would be stable.

As time passed, she progressed in her study of Taoism. As other people of political influence put faith in Buddhism, in accordance with her own instruction in Taoism, she demonstrated superhuman abilities and pulled off feats so unreal to the extent that in future generations, fictitious tales related to her became well-known. The legends that she left for future generations had this kind of behind-the-scenes to it.

Miko was not negligent of her final objective of achieving true immortality, but in the process, the cinnabar (mercury sulfide, a poisonous substance) that was supposed to bring about immortality, instead ruined her body. She made the judgment that she would not be able to hold onto her body like this and decided to become a shikaisen. However, Miko was afraid of implementing this all by herself. To test it, she asked Mononobe no Futo – though they were enemies on the surface – and Tojiko be revived. Therefore, she relied on having Futo going to sleep first.

After Futo continued to sleep without decaying, Miko performed the ritual on herself. Her plan was to reawaken once the nation had outgrown Buddhism, they awaited their revival in the time of seeking sainthood. Unfortunately for her, Buddhism dominated the Japanese people for over a thousand years. In actuality, since Buddhist monks repeatedly sealed Miko's mausoleum with the power of Buddhism, she was unable to revive. Her plan was foiled.

Since there was no need to be in a hurry, she continued to wait until the time of her resurrection. People in general started disbelieving in the feats Miko had performed. Currently, there are definitely no illusion-like powers like humans who display superhuman abilities, so it was inevitable that her exploits were suspected to be fictitious.

However, due to this denial of illusion, she and the mausoleum moved to Gensokyo. When Miko finally was about to be resurrected, it was after the entire mausoleum had been transported to Gensokyo. There were no temples, so it was always possible for her to prepare for the revival. However, just then, a Buddhist temple had been built on top of the mausoleum to prevent her resurrection, both due to bad timing and because the temple's head priest had concluded that powerful human rulers like her would be dangerous for the youkai. Fortunately, the act did more to revive her than otherwise; the mausoleum was finally broken, and the divine spirits that were attracted to Miko overflowed throughout Gensokyo.

Miko has very light, almost platinum blonde hair, styled like horns or ears, as well as grey eyes. She wears purple headgear which has been described as both headphones and earmuffs. They bear the Chinese character meaning "Harmony" (和 wa) which was used as the name of ancient Japan (Wa). When she’s not using the headphones, she wears a pair of earplugs with the same design[8]. Her clothes are a purple dress under a white vest with elaborate trimming. The colors used in her dress refers to the Twelve level cap and rank system: a famous political achievement that she (= Prince Shoutoku) made ("violet" represents 1st rank and "purple" for 2nd rank.). She holds a shaku and carries a sword which is assumed to be the Seven Star Sword (七星剣 Shichi-sei ken) - a Taoist sword known to be worn by Prince Shoutoku in this portrait - on her waist.

Miko has a few followers as part of her religion. Mononobe no Futo is an ally of Toyosatomimi no Miko. Futo acted as Miko's test subject during the process of immortality. Soga no Tojiko is an ally of Toyosatomimi no Miko. These two assist Miko during one of her spell cards.

Seiga Kaku is an ally of Toyosatomimi no Miko. Seiga was the one who taught Miko the charms of Taoism. Despite this, she feels Seiga would cause trouble down the line. Yoshika Miyako is a Jiang Shi controlled by Seiga who guarded Toyosatomimi no Miko's mausoleum during her resurrection; as of yet any interaction between the two have not been seen, whether in the past or present.

Miko and her allies initially had an antagonistic relationship with the residents of the Myouren Temple. The existence of a Buddhist faction led to the resurrection of the Hall of Dreams' Great Mausoleum. The Buddhist monk Byakuren Hijiri's Myouren Temple was built above Miko's mausoleum, obstructing her resurrection. Nue Houjuu, a resident of the temple, called in Mamizou Futatsuiwa in order to fight against Miko.

In the years since Miko's resurrection, she and Byakuren appear to have developed a mutual respect for each other. They worked together as partners during the Perfect Possession Incident, as did their followers Futo and Ichirin Kumoi. Futo suspected Byakuren betrayed Miko during the incident, but Miko assured her that while Byakuren may follow a different religion, she is not the kind of person who would do that.