While there is little that Satori can't find out about someone else, finding out her past is really quite hard to do. All that's known is that, an undefined amount of time ago, she traveled to Hell to get away from the people and youkai who loathed her for her power to read minds. In the ruins of the old Hell, she built the Palace of Earth Spirits and became one of the founders of the Ancient City. As such, she's considered the town's mayor, even if she denies having such responsibility.
A dour girl who comes from Hell, Satori knows that she is hated because of her power. She associates better with animals (and animal youkai) than people, and tends to surround herself with animals because they can't normally talk. Towards others, she comes off as cold or even snippy, seemingly interested in keeping to herself. Satori may seem boastful of her power, and she can't seem to help but share that she heard that thought. And that one. And that one, too. Considering she's such a recluse, it's a wonder she opened Hell's Hot Spring in the first place.
Due to the way her power works, Satori has become quite interested in costuming. There is a substantially large walk-in closet in the Palace of Earth Spirits, containing costumes derived from the typical outfits worn by most Gensokyo residents she has met or heard about.
As a result, she's also quite a good seamstress. This comes in handy when repairing her clothes or the clothes of her pets.
Satori only has a few spell cards of her own. Her real potential in combat comes from the experiences of her enemies. She is capable of reading her foe's heart and deriving spell cards on the fly based on those used by her enemy, or people that her enemy has fought in the past. These are called Recollections.
Satori's Recollections tend to be weaker than the real thing. However, her age and experience allows her to combine Recollections in unexpected ways, which can catch opponents unaware. She's very tricky to fight against, which makes up for her general weakness in combat.
Koishi Komeiji ~ Satori's beloved younger sister. Satori tries desperately to understand why Koishi sealed her third eye, and wishes to know how she did it. She wants, somehow, to undo it and reutrn Koishi to the way she used to be, so they could be inseparable sisters again. In the back of her mind, she fears that may be impossible. Talking with Yuugi helps her feel better about this, though.
Utsuho Reiuji ~ Nicknamed Okuu. Utsuho is one of Satori's two most precious pets. Since consuming Yatagarasu, Utsuho has become taller, but her personality hasn't changed much, to Satori's relief. She's still a fun and sweet girl, and one of the few people she knows who is both openly honest with Satori as well as accepts what she is. Sensing the love and adoration from Utsuho via her power always brightens Satori's day.
Rin Kaenbyou ~ Nicknamed Orin, Rin is the other half of the pair, as one of Satori's most precious pets. A hard working kasha, Satori relies on Rin to keep things organized and flowing. She depends on Rin, and often confides in her. Sometimes, she has to make Rin return the favor, and takes a little bit of delight in making the cat sweat when she thinks she's in trouble. In some ways, Satori is concerned that she might be taking advantage of Rin's dedication, and is liberal with "assigning" the kasha to take days off in order to make up for it.
Yuugi Hoshiguma ~ The strongest Oni Satori has ever met, and probably the strongest in the world. Satori has deep respect for Yuugi's strength as well as her wisdom, and often confides in the blonde when she is troubled. In turn, she offers advice to the oni when she can. She views Yuugi as a big sister, and the two get along quite well.
Mokou Fujiwara ~ An immortal human Satori met on the surface. Mokou doesn't seem to mind Satori's ability, and accepts her in much the same way as Yuugi and Suika do by just being open and honest with herself with nothing she tries to hide. Mokou has become one of Satori's closest friends on the surface, though Satori doesn't like to get involved in the rivalry Mokou holds with Kaguya Houraisen
Reimu Hakurei and Marisa Kirisame ~ While she is thankful to these two for rescuing Utsuho from herself, Satori is also extremely put off by the fact that Reimu immediately wanted to beat her up and Marisa wanted to steal things from her home. They are not allowed inside the Palace for these reasons.
Parsee Mizuhashi ~ The bridge princess who guards the Bridge No One Crosses. Satori is wary of Parsee, knowing she is driven by jealousy and has developed the ability to manipulate it as a weapon. However, the girl has been trying to socialize, and so Satori encourages it.
Yamame Kurodani ~ A tsuchigumo from the caverns above the Ancient City. Satori does not know her very well, but suspects the two would get along in much the same way Satori connects with other animal youkai.
Kisume ~ A bucketgirl from the caverns above the Ancient City. Satori enjoys her company, and in turn, seems to be the only person Kisume is comfortable talking to. Kisume helps out around the hot springs, despite her shyness. However, Satori doesn't know her very well.
Akane Chiyoko ~ The latest youkai addition to Satori's collection of pets, Satori adores the turtle girl's devotion, but as a new addition she has not yet identified Akane's personality type. She's also identified jealousy in Utsuho when Akane is around, and so is keeping her distance until the raven is comfortable with her.
Tenshi Hinanai ~ Tenshi has done plenty of things to raise Satori's dislike, chief among them being the direct harm of one of her pets. She's since worked it out by throwing the angel through a bridge, but doesn't feel the score is even yet. That was more of a lesson in why one shouldn't underestimate an old and clever satori.