Fight Anbu Kakashi
To be able to do this you must complete 40 of Kakashi's missions including the 'S' rank mission against Guy. Complete at least 20 of every other character's missions and then redo Kakashi's 'S' rank mission. When these tasks have ALL been completed his rival will be Anbu Kakashi instead of Gai.
More tricks, tips and cheats for this game are right here - Naruto Shippuden: Clash of Ninja Revolution 3 cheats
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