Successfully complete the indicated task to unlock the corresponding character:

Gaara: Successfully complete "Burning Will Of Fire" in Flashback Mission: Leaf 
Destruction Arc. 
Itachi Uchiha: Successfully complete "Fatal Encounter" in Flashback Mission: 
Tsunade Search Arc. 
Jiraiya: Successfully complete "A Match With Pervy Sage". 
Kabuto Yakushi: Successfully complete "A Whirling Rasengan Explodes" in 
Flashback Mission: Tsunade Search Arc. 
Kakashi Hatake: Successfully complete the Genin Training Arc. 
Kankuro: Successfully complete "The Aburame Clan" in Flashback Mission: Leaf 
Destruction Arc. 
Kimimaro: Successfully complete "Battle With The Sound Begins" in Flashback 
Mission: Sasuke Chase Arc. 
Kimimaro (Curse Marked Second State): Successfully complete "A Duel That Risks 
Their Bond" in Flashback Mission: Sasuke Chase Arc. 
Kisame Hoshigaki: Successfully complete "Toad Sage Shows His Ability" in 
Flashback Mission: Tsunade Search Arc. 
Might Guy: Successfully complete "Odd Beast Battles a Scourge" in Flashback 
Mission: Tsunade Search Arc. 
Might Guy (Eight Gates): Successfully complete "A Duel That Risks Their Bond" 
in Flashback Mission: Sasuke Chase Arc. 
Naruto Uzumaki (Nine-Tailed Fox): Successfully complete "A Duel That Risks 
Their Bond" in Flashback Mission: Sasuke Chase Arc. 
Orochimaru: Successfully complete "Sannin Rock Heaven And Earth" in Flashback 
Mission: Tsunade Search Arc. 
Rock Lee (Eight Gates): Successfully complete "A Duel That Risks Their Bond" 
in Flashback Mission: Sasuke Chase Arc. 
Sasuke Uchiha (Curse Marked Second State): Successfully complete "A Duel That 
Risks Their Bond" in Flashback Mission: Sasuke Chase Arc. 
Temari: Successfully complete "The Chunin Exam Sleeper Pick" in Flashback 
Mission: Leaf Destruction Arc. 
The Third Hokage: Successfully complete "Unprecedented Mega Battle" in 
Flashback Mission: Leaf Destruction Arc. 
Tsunade: Successfully complete "Tsunade Finally Opens Her Eyes" in Flashback 
Mission: Tsunade Search Arc.