The Earth is not just the world of humans. In fact, there are 1,500 aliens living among us, and the Interstellar Immigration Bureau handles matters related to aliens. Edwards (Will Smith), an ordinary New York policeman, joined this organization by chance and became a member of the MIB, codenamed J. From then on, he had no name or identity and became the partner of special police K (Tom Lee Jones). The first incident J dealt with was the invasion of the Zerg. Prince Rosper of Acheron was killed by the Zerg on Earth, and the "Galaxy" he carried with him, the best source of subatomic energy in the universe, was also missing. If the Zerg found it, it would bring a devastating blow to the Acheron people; the Acheron people issued an ultimatum that if the Earthlings could not hand over the "Galaxy" within an hour, they would destroy the Earth. For the safety of the Earth, K and J had to stand up.