Yamato attempts to introduce
the new Team Kakashi members to each other, but from the very start Sai
gets on the nerves of Sakura and Naruto and makes no attempt to conceal
it.
Later, Sai is delivered special mission
instructions from Danzou by a senior member of Roots. He is
reminded that in Roots, emotions are useless and only the mission
matters.
In a meeting in Kakashi's hospital room, Jiraiya
and Tsunade warn Sai about Naruto's dangerous new ability to unleash
the Kyuubi's power in a "chakra cloak" whenever his emotions run high.
It is for this reason that Yamato was specifically selected
for this mission.