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.
Sai was assigned to the disposal
of people dangerous to the Leaf...
Саю поручали избавляться от тех, 
кто представлял опасность Листу.