Matsurika Shinoji is the tritagonist of the story. She is Mariya Shidou's maid. She is generally silent but is usually quite rude when she chooses to speak. She delivers the vast majority of her lines with almost no facial expressions. The majority of her insults are directed at Kanako Miyamae and Mariya. She refers to Kanako by such names as "Ms. Pig," "Eiffel Tower" and "Tokyo Tower" due to Kanako's tall stature.
When speaking to Mariya, Matsurika often delivers sharp remarks in regards to his cross-dressing tendencies or sexual perversions. Matsurika also attends classes with Mariya. She also stays hidden from the rest of the students, and follows Mariya's orders when told. She has O blood type, is 162 cm tall and her birthday is in September 16th. A student of Ame no Kisaki class 1-A, Matsurika is a constant attendant of Mariya Shidō. It's unknown how long they have been together, but she has been seen when Mariya was very young. She knows of Mariya's secret identity as a male in an all girl's Catholic school, Ame no Kisaki. She is his closest friend, accomplice, and the only one who can openly mock him without reprisal. Both seem to enjoy teasing Kanako Miyamae. Her hair color is gray with long, curled pigtails and her eyes are yellow. She is always seen in a maid uniform with wooden platform heels. She often seems to work as Mariya's emotional center. Questioning him about his relationships with his twin sister, Shizu; and his elder cousin, Ayari. She has a twin brother named Rindou.
When Kanako discovered Matsurika dressing Mariya, she played the victim in Mariya's plan to blackmail Kanako for her silence. Mariya had ripped open her dress to expose her bra and breasts. She tends to tease and order Kanako around. When Kanako realized that Matsurika was a student in Ame no Kisaki she tried to demand some respect from as an upperclassmen, but this only caused Matsurika to giggle, to which Mariya showed great shock. Though in front of other students both Mariya and Matsurika play their role as underclassmen to Kanako.
Once, with no provocation from Mariya, she struck an unsuspecting Kanako with a basketball. When asked she told Mariya she felt the need to fix an error before it reached the point of no return.
When Ayari's dress accidentally ripped open, in the front, exposing her breasts to the festival crowd. Matsurika covered Ayari. Though what seemed like a generous action took a twist when she made Ayari understand just how embarrassing her exposure was, commenting on how it's not as if she was a child, but her large lumps of flesh, that are her breasts, were shown to everyone present. Ayari ran away, cursing Mariya; and locked herself in a room. This had shattered the near reconciliation between Mariya and Ayari. She seems to have the ability to read Mariya's mind, and the two communicate through telepathy at times.
- Though she is always with Mariya. It's unknown where she sleeps since there are only two beds in the dorm room Mariya shares with Kanako.
- Matsurika has been shown with Mariya as a young child, but it is never explained when they first met.
- During Episode 11 of the anime, "Offerings to God" (Kami e no Kumotsu), Matsurika breaks the fourth wall, with Mariya; and comments on the notes that had been appearing throughout the whole episode saying, "It's like a bad episode of Ghost in the Shell.", another anime series.