In the ancient times of Japan, waaay before Gensokyo was even a thought, Suwako was a native god who ruled her own kingdom. She was able to tame the Mishaguji, very powerful curse gods, and received an enormous amount of faith. However, other gods of ancient Japan tried conquering her kingdom, saying they would unify all of their conquered countries. One of these gods was Kanako. Of course, Suwako resisted these other gods and fought back with the finest steel weapons of the time. However, Kanako held out a thin vine and, demonstrating the difference between their divine powers, rusted her entire arsenal. Suwako understood and valiantly relinquish her kingdom. Naturally, however, the people of her kingdom could not forget their fear of the Mishaguji, which Kanako did not control. Thus, they could not accept her. After some shenanigans with homophones involving Suwako's surname and a vestigial god, Kanako borrowed her powers and quietly ruled as God of Mountains. Suwako, meanwhile, regained rule over her kingdom. And somewhere down the line, she got with a human. That started a line of demigods that served as priests and priestesses at the Moriya Shrine. As you may have guess, however, this did not last forever; less and less people were believing in gods, which panicked Kanako. To solve this, she moved the shrine, along with Suwako and Suwako's latest descendent, Sanae, to Gensokyo.
Despite her diminutive appearance, she's not very childish (though that's not to say she doesn't like to act like it sometimes, especially during the cold months). Her personality can be considered caring (when she feels like it), valiant (in the face of real danger, anyway), respectful (to those she's sucking up to), passionate (about her descendents, the Earth, partying, and whatever she feels like doing), and hard to enrage (though it is rather explosive). A true benevolent goddess, at least when nobody's (sans Sanae or Kanako) watching. When they aren't (or she's just feeling relaxed)? Well, she can be rather silly.
...okay, let's get serious. While the above is true, there's still a side of her it only scratches. Back to her anger; if you do manage to press her berserk button, you can pretty much finish your will if you can't take gods. Even if you're not human. If she threatens you seriously? She will (99.6% of the time) hit all the right notes and will make you submit to her. She's a schemer, full of deceit and lies. Ready to hit where it hurts, play dirty at any time. The world of the gods is a tough place. How do you think she managed to tame the Mishaguji when many had failed? Not through pure power. Luckily, this side of her rarely appears except when it needs to. Or when it accidentally slips out. Though, that's when she joking around. Usually.
Ability: The creation, manipulation, and removing of earth. She also has control over native (well, not to Gensokyo) curse gods called Mishaguji.