The Ultraman (1979)

In the 21st century, humanity is threatened by rampaging monsters of unknown origin. Officer Chouichirou Hikari of the Science Defense Squad is bonded to Ultraman Jonias, an alien from the planet U-40 who has been tasked with defending the planet Earth. The joined heroes face many foes while maintaining a secret identity. The actual threat is a planned alien invasion by the Heller Empire, a renegade faction of Ultra People.