As a city was being destroyed by a massive space monster, panic-stricken people ran for safety, including five high school students named En, Kai, Shin, Yoku, and Ryu. Despite their efforts to escape, they found themselves trapped and decided to seek refuge in a nearby patrol car. Unfortunately, the monster was fast approaching and they resigned themselves to their fate. Suddenly, the patrol car glowed an eerie blue-white light and vanished into thin air, leaving the students bewildered and disoriented. To their amazement, they were transported to a strange world where they met an alien named Bravian, an officer of the Space Police Organization tasked with maintaining peace and order throughout the universe. Bravian revealed that he was being hunted by dangerous aliens from the Space Prison Sargasso and had entrusted the students with a powerful weapon called the "Dag Beagle". This machine was created by copying technology from Earth and was designed to fight against the Sargasso aliens. With Bravian's help, the students transformed into the mighty Dagwon and began battling the ferocious space monsters. In a dramatic turn of events, En found himself merging with the patrol car to become the powerful Brave Robot Dag Fire, ultimately defeating the enemy. However, their fight against the Sargasso aliens had just begun, and the Brave Dagwon would have to confront their villainy head-on.