Suika is the only oni currently living above ground in Gensokyo, with the remainder of the oni race living underground. Just as the folktales say, she has two horns on her head that symbolize her oni heritage, and enough physical strength to throw large boulders single-handedly. Her personality is jolly and quite childish as you would expect from her appearance. She also likes to drink and loves to party with all her heart.
Her power in the games is to manipulate density.
(Source: Touhou Wikia)