This is Rima Mashiro.
The girl serving as the new Q-Chair, she is the same age as Amu. Rima
is a short, cute and beautiful girl with a selfish personality. She is
well-liked among male students and disliked by female students, such
as Amu. She feigns crying to deceive people. At one point of the
manga, while looking for X Eggs with Amu, she Character transforms and
destroys one unnecessarily.
Her Character Transformation with Kusu Kusu is called "Clown Drop."
When she does Character Change she becomes a gag character which she
dislikes. The words 'Bala-Balance' spark her Character Change.