Ultraman Justice was first seen rescuing Ultraman Cosmos in the movie The Blue Planet. He was simply referred to as a "legendary giant" whose goals obviously were similar to those of Cosmos.
Some time later, though, Justice was directed to destroy the Earth; a universal intelligence feared the humans, once they began to go into space, would endanger the rest of the universe. This put Justice into conflict with his former friend, Cosmos. During this conflict, Justice took on a new form, Crusher mode, which gave him more than enough strength to overcome Cosmos. Justice also took on a human form, that of a raven-haired woman named Julie (also pronounced "Jury" in Japanese). Musashi, now hosting Cosmos once again after his initial battle with Justice, convinced Julie/Justice that humans were not the dire evil she had been led to believe.
When the intelligence sent its own forces, as an armada of ships, Justice and Cosmos faced the attackers together in space. Blown into the atmosphere by the attackers, and unable to regain control of their fall, both began to glow red with atmospheric friction as they reentered the atmosphere. Justice was willing to sacrifice his own well-being for Cosmos by moving his own body between Cosmos and the atmosphere, taking on so much heat that his body began to melt. A final blast from the attacking ships, however, tore through both heroes.
Unbeknownst to all but two friendly aliens on Earth, though, the blast that "destroyed" both Ultramen allowed them to merge into one being, Ultraman Legend. Legend destroyed the attacking ship, drawing the attention of the universal intelligence. Separating back into two healthy Ultramen, Justice and Cosmos convinced it that the humans were not the danger they had believed.