|Forgathering dream, illusion, therefore a night parade of a hundred demons|
Location: Some hidden country occupied by oni (currently she's living somewhere in Gensokyo)
Ability: Manipulating density and sparseness
There are supposedly no oni in Gensokyo, but this girl insists that she is an oni.
Oni are generally jolly and love to drink, feast, and compete with humans in any kind of contest, from simple melee to drinking games. When they find a human that they like, they tempt that human into challenging them in any way the human desires. Should the human lose, they are abducted.
The oni find these games to be great fun, but humans don't appreciate the nature of that fun. Put simply, humans cannot compare to an oni's level of ability. Humans could enjoy themselves as much as the oni if they tried to reach the power level of their opponents, but they don't. Worse still, humans attempt to destroy the oni with underhanded tactics.
Abduction by oni used to be a symbol of human fear, which was the oni's reason for their existence. In a way, that fear was necessary to the human race... Yet, the humans selfishly put an end to it.
The oni, growing weary of being duped and killed repeatedly, abandoned humans for all time and moved to a place beyond human reach, or so the legend says. In any case, the oni have not been seen since.
This girl insists that she is an oni.
She is certainly jolly and loves drinking, and likes feasts so much that she has them every 3 days. The reason for that is given in-game, so I won't mention it here. But to tell the truth, she wants to restore the relationship between humans and oni. Now why did that fail...? That's also mentioned in-game, toward the end.
As mentioned above, Suika is jolly and drink loving. Innocent and simple-minded. She raises an upbeat atmosphere in a crowd, but when you're alone with her, you'll gradually become irritated by her childishness.
Her ability allows her to control density. She can gather and scatter whatever she desires. By gathering people's sentiments, they will have parties; by scattering herself, she can become as mist. The strange mist that brought about the events of Immaterial and Missing Power was none other than herself, in very thin form. Her ability does not produce some unseen power; she can gather and scatter only that which already exists, but the process occasionally transforms one thing into something completely different. It's kind of close to creation in that way. The long lost power of the oni is truly exceptional.
Her physical ability is outstanding as well; her strength, speed, and mystic power all far exceed that of a human's. Her sole weakness is her small stature, but she compensates for that in many ways. Since she loves competition against humans, she is quite tough even when she is drunk. That is to say, the more drunk she is, the tougher she becomes. Or rather, there's hardly a time when she isn't drunk.