This is Japan's first colour science fiction film, produced in 1956 in the wake of the success of Gojira. It was called Uchûjin Tôkyô ni arawaru (Spacepeople Appear in Tokyo), but was not dubbed into English and released in America until 1967.
Planet R is on a collision course with Earth, and starfish-shaped aliens from the planet Paira take on human form to warn us and help Japanese scientists prevent the collusion.
Despite the utter cheapness and ridiculousness of the alien costumes (yes indeed, they pretty much look like how they look in the poster, although human-sized, not building-sized), this is not as cheesy or campy a film as many of the later Japanese monster movies are.
At least, it doesn't try to be.
But can you take a film with aliens as stupid looking as these seriously? If you think you can, this might be worth a look. It had a large budget and fairly decent production values. It even has a couple of big dance sequences. There's not a lot of special effects, but what there are passable for the time.
Interestingly, it is the use of atomic weapons that saves the day in this film, quite the opposite to the usual attitude of Japanese monster movies in which it is nuclear weapons or accidents that cause the problem.
Sharp-eyed viewers will notice a whirly prop in the first scene. A similar one shows up in the first scene of 1978's Superman.