Ekaterina Kurae, often referred to by her nickname 'Katja', is a central character in the anime series 'Seikon no Qwaser'. She is a powerful Qwaser who wields the element of copper. Despite her young appearance, Ekaterina is highly intelligent and manipulative, often using her doll-like charm to deceive others. She has a sadistic personality and takes pleasure in controlling those around her. Ekaterina serves as both an ally and antagonist in the series, her actions motivated by her own mysterious goals. Her complex character adds intrigue and depth to the storyline.