Itsuwa is a Japanese magician of the Amakusa-Style Remix of Church. Hailing from the town of Itsuwa in Kyūshū (later merged into Amakusa City), she likely spent most of her life in Shimabara, Kyushu, alongside her comrades. Specializing in the Amakusa's discreet magical practices, she blends Christian, Shinto, and Buddhist elements, utilizing everyday items and symbolism to conceal activities. Her background includes involvement in developing the "Saint Destroyer" spell, designed to counter Saints like Kanzaki Kaori following Kanzaki's departure. In appearance, Itsuwa has shoulder-length black hair (depicted as purple in visual media) styled in a bobcut with short fringes and light brown eyes. She possesses a well-endowed figure described by comrades as "hidden." Her typical attire consists of practical clothing like a sleeveless tank top with capris or a tank top over a sweater with modified pants for blending into surroundings. Mission circumstances, such as rescuing Kamijou Touma from a river in Avignon, have forced her into skimpy clothing. Estimated to be a minor due to her inability to legally consume alcohol, she is around Touma's age. Itsuwa exhibits a warm, modest personality marked by shyness and humility. Skilled in domestic tasks like cooking and housework, her culinary abilities impress characters such as Tsuchimikado Maika. She harbors romantic feelings for Touma, often expressing them through subtle gestures like offering hot towels, though shyness prevents direct confessions. Unlike other female characters close to Touma, she avoids violent outbursts when upset, favoring softer, lady-like reactions. She experiences jealousy toward rivals like Kanzaki while maintaining deep respect. Emotionally sensitive, failures—such as being unable to protect Touma from Acqua of the Back—trigger severe depression requiring comrade intervention like Saiji Tatemiya's. During missions, she shifts to a serious, reliable demeanor, emphasizing teamwork central to Amakusa combat philosophy. Her combat centers on the Friuli Spear, a five-part weapon disassembled for concealment and reassembled during engagements. She wields it with high proficiency, often employing teamwork tactics. Unique spells include "Saint Destroyer," exploiting the Idol Theory weakness of Saints by mimicking the Lance of Longinus; this requires formation with other Amakusa members and specialized components like a friction-reducing towel. Other spells encompass "Seven Blades of the Seven Teachings" (multidirectional attacks using seven steel wires), ley line disruption via symbolic objects, healing magic, damage-transference charms diverting injury to clothing, "Icy Night Wind" (asphalt-shattering explosions), "Reproductivity that Plants Possess" (reinforcing spear durability), and "White Explosion" (dual-location light attacks). She also utilizes life-force concentration spells and mandala-based illusions. Itsuwa played pivotal roles in major arcs. In Avignon, she rescued Touma from drowning and aided his mission to destroy the Document of Constantine, facing Terra of the Left. Later, she served as Touma's live-in bodyguard against Acqua of the Back, posing as a transfer student to infiltrate his school. During this assignment, her cooking for Index and Touma alleviated household tensions. Her protective duties culminated in a confrontation with Acqua, who critically injured Touma and issued a deadline to sever his right arm. Itsuwa attempted healing magic, negated by Touma's Imagine Breaker, highlighting her emotional investment in his safety. Comrades frequently supported her romantic pursuits, manipulating situations to encourage her relationship with Touma.