Voiced by: Yoshitsugu Matsuoka Sorata is the male protagonist of the story. He is a second-year later third year student of Suiko, who lives in room of Sakura Dormitory. He was kicked out of the regular dorms after he chose not to give up a stray cat he found he cannot resist taking in stray cats, and he ends up keeping seven of them in his room. As many of the Sakura Dormitory residents have outstanding grades and art skills, he often feels plain and normal among them.
Chihiro, the dorm supervisor, chooses him to take care of Mashiro, the "pet girl" referenced in the title, and he is, understandably, reluctant to do so but ends up getting used to it. At the end of the thirteenth novel, he confesses to Mashiro. Sorata decides to become a computer game designer, but his game proposal to a famous computer game company is repeatedly turned down. In the sixth novel, he decides to make a game on his own.
A major plot of the story is how his personality and self-expectation evolves. She is the resident of room , as well as a world famous artist who transferred into Suiko as a second-year to learn how to draw manga.
Although her artwork is widely admired, she knows nothing other than drawing and has an extreme lack of common sense and living ability. Due to this, Sorata is forced to "adopt" Mashiro and help her out with the basic tasks of everyday life that everyone else takes for granted; he even has to pick out underwear for her to wear or she will go out without them. Her focus on what she wants to do, draw manga, awes Sorata and inspires him. She has very bad grades, since she cannot pay attention in class, but she can still pass the make-up exams by photographically memorizing all of the answers with her art talent.
In the third novel, Mashiro starts to develop feelings for Sorata and she even claims that she cannot live without him. According to Mashiro, she plans to live in Sorata's house and work as a manga artist after graduation. Although she is harsh to Sorata, she actually has a crush on him, and everyone aside from Sorata has noticed this.
