A local ice fairy in Gensokyo. For some reason, she fancies herself the greatest fighter in all the land...a blatant fib. Fairies in Gensokyo aren't THAT strong. Then again, Cirno is much stronger than the average fairy...but that's about it. Her childish aggression very often gets her hiney handed to her. She's not very bright, either - one can escape her by giving her a riddle. She'd take FOREVER to figure out the answer!
As expected, she can manipulate ice for a variety of danmaku attacks. She can utilize her Perfect Freeze ability to instantly encase anything in ice, even her danmaku, making them all slip in different directions. She's even manifested gigantic projectiles with her ice magic...!
One of her pasttimes is freezing frogs in the lake. She claims that it's purely to practice her ice powers. Certainly not because frozen frogs are cute or that their croaks annoy her or that juggling frozen frogs is thrilling due to the risk of breaking them...