Team Kakashi are stunned to learn that Sai's true mission is to kill Sasuke.  Naruto wants to believe that the smile Sai showed them was real, but there is a possibility that it was all an act.
After all, he said earlier that
he was going to save Sasuke...
.لقد قال قبل قليل أنّه ذاهب لإنقاذ ساسكي
Er hat doch eben gesagt,
dass er Sasuke retten wird.
Si él me dijo que iba a salvar a Sasuke...
¡Pero me prometió que salvaría a Sasuke!
Insomma! Prima mi ha promesso 
che avrebbe salvato Sasuke!
Ele disse antes que ia 
salvar o Sasuke...
Он ведь говорил, что спасёт Саскэ...