In Boukenger, if there were any two of the Negative Syndicates who fought each other more often, it was with Gaja and Ryuon. Their rivalry began in Task 2 when Ryuon was after the Gordom brain, but Gaja being a sneaky wizard always had something on his sleeve. He trapped Ryuon and thus began their hostilities. Of course, the hostilities are never without a price as whenever the two met, it was ALWAYS involving treachery. So what's the deal? Gaja had a sharp, sarcastic attitude like Tranza and Ryuon, well he was a major Sentai SOB like Radiguet (but to a lesser extent), which he was always more cruel. Gaja was more on the manipulative, sarcastic side while Ryuon was revenge-obsessed. Both villains were insane nonetheless. Ryuon like Radiguet always held a deeper grudge. So they did work together in Tasks 10-11 but Gaja managed to steal the secret of Leon Giordana's engine for himself, which of course angers Ryuon. Think like how Tranza managed to sneak a piece of Meteor...