When Shizuma first became Etoile with Kaori, her partner, she's been very cheerful and lively. However, since Kaori's death, she's been locked up in her room always and the cheerful and lively character turned to depressed, almost blank. She was very hard to read and predict which somehow annoys Miyuki Rokujō. Much of the time, she doesn't enjoy the dull work of the Etoile, so she often finds ways to skip her duties.
She met Nagisa Aoi and behavior changed once again, much to the student council's surprise and mostly Miyuki. The lively Shizuma somewhat came back again and her naughty, playful personality.
She also has a kind of playgirl attitude as seen in the series. Once, Nagisa saw Shizuma in the woods with another student whom she was about to kiss but was interrupted and the student had ran away with a flushed face.