|Name in Japanese||ケイト・ヴァレンタイン|
|Rōmaji Translation||Keito Varentain|
|Debut (Anime)||Episode 01|
|Appears in||Anime, Manga|
|Voice Actor (Japanese)||Yoshiko Sakakibara|
|Voice Actor (English)||Laura Chapman|
|Affiliation/s||Order of Magdalene|
Kate Valentine (ケイト・ヴァレンタイン Keito Varentain ) is the Head of the New York Branch of the Order of Magdalene. She is a strong willed woman who often seems out of place fighting demons and devils. She leads the order with an iron resolve, making sure the New York Branch Office runs as smooth as clockwork. For the most part she is the same throughout the anime and manga with major differences in character development.
Throughout the progression of the anime, Kate becomes more and more fond of Rosette up to the point that by the middle of the series, she repeats her lines and even begins to appreciate Rosette's optimism and sense of hope. However Rosette's death changes her character sharply. After Rosette was discovered dead with Chrono, Sister Kate leaves the order as a gloomy person. Her faith in God is permanently impaired and she is found stating that Rosette was a far more devout Christian than she and anyone else in the Order and asks herself why Rosette had to be the one to sacrifice her life to stop evil.
Like in the anime, Kate becomes more and more fond of Rosette, showing traits of Rosette's personality by the middle of the Manga. She is portrayed as being more involved in the field, commanding the Order's militia on several occasions. She gets demoted from her position as a result of the failure to stop Aion from bringing destruction to the East Coast. However she happily accepts the demotion, stating she no longer wanted that position. By the end of the Manga, her character changes, but it is the opposite of the anime. Rather than becoming a gloomy person, she becomes softer and more laid-back.