A planet mentioned in Ultraman Mebius, it was the world that Ultraman Hikari fell in love with but ultimately fell to Bogar's rampage.
Planet Arb, a completely peaceful planet, that hadn't had a single conflict and had been prospering for tens of thousands of years. Hikari arrived on the planet, being surprised by its beauty. Suddenly, the crystals in Planet Arb started floating, making the form of a humanoid figure. This being presented herself to Hikari, and believed that he was an Ultraman. Hikari said that he was not one of them, because he doesn't have any fighting skills, but Arb trusted him because of his pure heart, which was also like hers. Hikari told the being that he wanted to stay on the planet. The being of Arb denied him, explaining that the peace on Arb was only temporary, and soon a great disaster would occur that would destroy the planet. But a hero with the Armor of Light would arrive from the heavens at that time, and he would fuse with the soil of Arb and be called Tsurugi, and would defeat the destroyer. These sayings were known as the "Prophecy of Tsurugi" which foretold the end of the peaceful planet. Hikari said that he would become a hero and protect Arb, and flew to another planet.