Age: 17
Birthday: June 13
Zodiac sign: Gemini
Blood type: A

Mashiro is the female protagonist of the story. She is the resident of room 202. She is a world famous artist who transferred into Suiko as a second-year to learn how to draw manga. Although her artworks are widely admired by the world in spite of her young age, she knows nothing other than drawing, and has an extreme lack of common sense and living ability. Due to this, Sorata is forced to handle Mashiro's living chores, to the point that he even has to pick out underwear for her, or she will go out without them.

She has very bad grades, since she cannot pay attention to the class, but she can still pass the make-up exams by remembering all of the answers with her art talent.

In the third volume, Mashiro starts to grow feelings for Sorata, and she even claims that she cannot live without him.

In eighth volume, Sorata confesses his feelings for her.

In the ninth volume, they are officially a couple.

In the end of volume 10, they break up.

In the next chapter, there is a 4 year gap and they get back together again.

It is heavily implied in the last volume of the novel that Mashiro and Sorata had a child.