How do you unlock Gai in Naruto-Arena

First of all you have to complete "Team of Gai" (Missing-nin) and after that you have to complete de mission "Team 9 The Best Taijutsu Team" (ANBU)

• Win 15 battles with Rock Lee versus any Konoha Ninja who is not part of Team 9. (15/15)
• Win 15 battles with Tenten versus any Konoha Ninja who is not part of Team 9. (15/15)
• Win 15 battles with Hyuuga Neji versus any Konoha Ninja who is not part of Team 9. (15/15)]