"Admiral Zheng He sailed past Singapore during his voyages, and was purported to have used a rock structure located close to Labrador Park, as a navigational marker. The rock structure known as the Longyamen or Dragon Teeth's Gate was however destroyed in the 1880s by the British Navy to widen the channel to the Keppel Straits."
Unknown to all that have seen it, the "rock structure" was actually the tooth of a dragon which has lay dormant in the area for more than 800 years. In ancient times, the dragon went out of control and began using its powers for destruction. A wise shaman cast a spell on the dragon and put it to sleep for eternity. When its tooth was blown up, the dragon was killed, but its body was magically preserved due to the powerful magic of the shaman.
The British Navy, after blowing it up, brought some pieces back to England for display. During World War II, the Japanese Imperial Army discovered some of the remaining pieces of the tooth and brought some back to Japan and put it on display in the Tokyo Museum.
Creator King Ryuuwon of the Jaryuu clan discovered the dragon and ordered his followers to rebuild the dragon with robotic parts, turning it into a cyborg, but they lacked the pieces of the tooth, which were now scattered over the world. They sought to find all the pieces of the tooth, and seal the Earth's fate.
Sargess Japan anticipated this event and sent out warnings to all Sargess departments in the world. However it was too late, as Jaryuu had all the pieces of the tooth, except for one - which neither Sargess nor Jaryuu knows where it is. To be able to protect this piece successfully, Sargess International Headquarters (Singapore) ordered all its five Boukengers to return and team up to find the treasure, and defeat the Jaryuu.