Rita is the main character of the series, a twenty year old former assassin of Dutch origin who was known in the underworld as the Witch and designated as Convict No. 999. Her background is one of profound isolation and violence; trained from a young age to be a merciless killer, she spent much of her life alone before being incarcerated, where she was initially known only as Jane Doe. Her current employment at Kindergarten Noir is a form of witness protection or sentence reduction program, where she works as a teacher of the Dandelion class in exchange for protecting the children of the world's elite from constant assassination attempts.

In terms of appearance, Rita is of notably small stature, often teased by her colleague Doug as a little twerp. She has brown hair that she typically wears in a simple ponytail, with uneven long fringes falling just above her green eyes and side bangs reaching past her shoulders. Her work uniform as a kindergarten teacher consists of a long sleeved white polo shirt, a black necktie, and an apron marked with the word for dandelion.

Rita's personality is defined by a stark and often humorous contrast. On the surface, she presents a friendly, warm, and approachable demeanor, especially when interacting with the children in her care. She is physically strong and eager to participate in their games, though she can become genuinely anxious and uncertain when dealing with tantrums or other typical childcare challenges. However, this cheerful exterior masks the cold and efficient killer within. When focused on a mission, she becomes deeply intimidating, eliminating enemies with a chilling detachment that treats them as insignificant, a side of her that has even terrified her fellow teachers.

Her most prominent and driving motivation, however, is her desperate desire to find a romantic partner. Rita is a self proclaimed hopeless romantic who wholeheartedly believes in horoscopes, blood type compatibility, and the concept of soulmates. This obsession directly impacts her role in the story, as she has a notable weakness for handsome men. When confronting attractive male assassins, she has a peculiar habit of momentarily giving them a chance by asking irrelevant questions about her preferences; if their answers do not align with her tastes, she then kills them without hesitation. If they are not handsome, she dispatches them immediately.

Her key relationships are central to her development. She works closely with her colleagues Doug and Hana Bradley in the Dandelion class. Doug, a former swindler, is her superior and a frequent source of bickering, though their relationship becomes more complex after an accidental kiss, leading Rita to see him as something more than a colleague, even as misunderstandings persist. Hana is her junior, and the two share a strong bond of trust. The school's director, Erina Winkler, is a source of immense intimidation for Rita, as she is fully aware that failure in her mission to protect the children would result in her own death. Rita also has a twin brother named Leo, a member of a跨国犯罪组织, though the reasons for their estrangement and her departure from her family are not fully detailed.

Rita possesses superhuman physical abilities that make her a formidable fighter. Despite her petite frame, she has incredible strength, capable of handling heavy weapons and large objects with ease, and can leap from great heights without injury. Her speed and reflexes are imperceptibly fast, allowing her to dodge surprise attacks and even react to bullets at close range. She also demonstrates extraordinary durability and near inexhaustible stamina, able to endure punishing blows and fight for extended periods without tiring. She is a master of hand to hand combat and proficient with virtually any weapon she can find, from guns and swords to everyday objects like scissors or shovels. Despite this power, her significant weaknesses are her aforementioned attraction to good looking men, which can compromise her focus, and her inability to swim.