Ultraman: Towards the Future (1990)

Jack Shindo and Stanley Haggard are members of the first manned expedition to Mars, and on the red planet find a giant slug-like monster, Gudis. Suddenly the giant warrior, Ultraman (Great), arrives and fights Gudis, but is knocked down for a period. Jack Shindo is pinned by a rockslide and Haggard tries to escape in their ship but is blown up by Gudis. It is then that Ultraman gets up, and when he is on the verge of victory Goudes changes into a virus and travels to Earth, where it plans on corrupting all life, mutating other creatures into monsters and awakening existing ones. Needing a human host to survive on Earth, Ultraman joins with Jack, allowing him to become the mighty alien when all seems lost. He joins the Universal Multipurpose Agency, or UMA, in order to help them battle the many monsters that threaten humanity.