The B Rank Missions are only assigned to to experienced ninja. With these missions you are able to unlock villians and subordinates of the most dangerous ninjas.
Win 15 battles with Nara Shikamaru versus any Sound Ninja. (15/15) Win 15 battles with Yamanaka Ino versus any Sound Ninja. (15/15) Win 15 battles with Akimichi Chouji versus any Sound Ninja. (15/15)