Kaname is worried about never seeing Mary with friends from her class.; Mastushita assumes she has lots of friends.  But what does Mary think?
I guess the top student of your class
 doesn't just spend all day studying.
Supongo que el mejor de la clase 
no solo se la pasa estudiando.
Supongo que el mejor de la clase 
no sólo se lo pasa estudiando.
Pelo visto o melhor aluno não fica
 só o tempo todo estudando.