Meet Forrest, a Pro Ranger hailing from the Almia Region. As a child, he was injured helping Pokemon escape one of the violent clashes between Thundurus and Tornadus. He was rescued by Landorus, who took a shine to him, and the two had been close friends while Forrest undertook tests to become a Pokemon Ranger.
It would be years later, during a mission to stop artificially created weather phenomenon, that they discovered Landorus was held captive and bound by a machine to use his power. He was freed by Forrest and his companions. Embarrassed at his body being manipulated out of the cloud of energy and exposed, Landorus was comforted by Forrest, the two forming a bond.
Despite his legendary status, the Ranger Guild recognized the unique situation, and Forrest and Landorus were officially made a team. Forrest took it upon himself to start going barefoot as a symbol of their equality, while Landorus turned his Partner Scarf into a makeshit fundoshi to avoid scaring the other humans with his otherwise exposed cock.
The two are definitely close, as the other rangers can attest... they tend to fool around quite often, as it turns out Landorus is a rather... kinky Pokemon.