SideSouder was a young man from Kyoto who was taking a motorcycle tour across Japan when he found a magic stone that permanently transformed him into SideSouder, an armored samurai with the spirit of the mythical Kirin and the power of thunder. In his new form, SideSouder still rides his motorcycle across Japan, fighting evil wherever he finds it. And on his travels, he discovers new powers based on the legendary Guardian Beasts. Seiryu the Dragon gives SideSouder a blue mode with water powers, Suzaku the Phoenix gives him a red mode with fire powers, Genbu the Tortoise gives him a green mode with earth powers, and Byakko the White Tiger gives him a white mode with wind powers. And when the cherry blossoms bloom in Kyoto, SideSouder can access a pink Sakura mode with light powers. With the start of the Reiwa era, SideSouder can now access a new silver mode with iridescent lightning powers. SideSouder later gained a golden form based on the Kouryu the Yellow Dragon which also unlocked new Spirit Armor upgrades for his previous forms.
With the Year of the Rabbit, SideSouder has gained the rabbit based Usagi form.