Duklyon is the name of a bakery at the elite Clamp School. But behind the scenes it's the headquarters for a trio of superheroes also known as Duklyon. When music blares over the loudspeakers the heroes jump down a chute inside an oven to their secret lair. Kentarou Higashikunimaru and Takeshi Shukaido are childhood friends who excel in different areas of athletics (track and field for Kentarou, kendo for Takeshi) and they do most of the physical work. The group is headed by Eri Chusonji, who rarely gets her hands dirty but is all too ready to beat up Kentarou and Takeshi over their antics by hitting them on their heads with a mallet. Then there's the mysterious General, who issues out Duklyon's missions.
Duklyon battles the evil Imonoyama Shopping District, whose goal is world domination. This group is headed by Kotobuki Sukiyabashi, a shy good-natured classmate of Kentarou's and Takeshi. The Imonoyama Shopping District goes to unique ways to ensure their goals; taking various classes hostage, hijacking the lunch room, and even kidnapping Utako Okawa, the Elementary School's student body president. But Duklyon always shows up to save the day.
Both Kentarou and Takeshi dress up in Metal Hero-esque outfits (Kentarou in red, Takeshi in blue) while they're fighting. However, they don't go by codenames and frequently yell each other's names in battle. Eri dresses in a skimpy space suit (with no mask) and Kotobuki wears a large eleborate outfit (with no mask). Even the General is very obviously Imonoyama Nokoru (leader of the Clamp School Detectives), though wearing a large pair of sunglasses. Despite this, all of them manage to keep their secret identities a secret from the general public (and Duklyon doesn't know who the General is).