This show was awesome! I never saw the original Japanese version, but I have seen the American version, called Masked Rider. The only reason I know of its original Japanese name is because of reading about Masked Rider on Wikipedia. However, if the Japanese original version is anything close to the American version, it is one AWESOME show. In the the American version, it is about this teenage alien who arrives on earth after escaping an enemy alien's attack on his home planet. He comes to the earth in a meteor-like spaceship and gets "adopted" by a human family. He uses his special powers to then protect the earth from the evil aliens.

Here's a pic of the hero character in his Kamen Rider suit, and wielding a beam sword.