Today is the cultural festival and everybody is doing their part.  Masaki is practicing hard as her role as the mouse in Cinderella to impress Shun.
I think she'll be disappointed 
by your stupidity.
Creo que se decepcionará de tu estupidez.
Creo que se decepcionará de tu estupidez.
Acho que o que decepciona ela é sua estupidez.