Natsuo Ishidō (石堂 夏央 Ishidō Natsuo) is the series' main protagonist. She is naturally talented at everything she does. Having lived with this ability her whole life, she cannot understand why other people cannot do things which she can do.
Natsuo's natural talent has given her a condescending attitude against her opponents, who she goads and teases during their match and after Natsuo's inevitable victory. She is ruthless when fighting, whether or not the fight is a serious one. Natsuo believes that people with the ability to be the best without even trying have the hardest time, since they don't have anyone to bond with and their whole life is one big competition. She is lonely and yearns for someone who can defeat her and give her something to actually work for. However, she doesn't voice her loneliness. Natsuo seems to fear her brother.