"Double-J" is a comedic anime series that revolves around the eccentric and often absurd activities of the Jitensha Jozu Club, or "Bicycle Skill Club," at a high school. The club, led by the overly enthusiastic and self-proclaimed "bicycle god" Joutarou Jomuro, is dedicated to mastering bizarre and impractical bicycle tricks. Despite its name, the club has little to do with actual cycling skills and instead focuses on outlandish stunts and performances that defy logic and physics.

The narrative centers on the club's attempts to gain recognition and members, often leading to chaotic and humorous situations. Joutarou, the club president, is a delusional yet charismatic figure who believes in the superiority of bicycles over all other forms of transportation. His unwavering passion and eccentric ideas drive the club's activities, which range from attempting to ride bicycles on water to creating elaborate, Rube Goldberg-like contraptions involving bicycles.

Other key characters include the level-headed and skeptical transfer student, Aoi Fukuyama, who reluctantly joins the club and often serves as the voice of reason amidst the chaos. Despite her initial reluctance, Aoi gradually becomes involved in the club's antics, often finding herself caught up in Joutarou's grandiose schemes. The club also includes a small group of equally quirky members, each contributing their own unique brand of humor and absurdity to the group dynamic.

The series is episodic in nature, with each episode presenting a new, increasingly ridiculous challenge or goal for the club to tackle. These challenges often involve interactions with other school clubs or external characters, leading to a variety of comedic scenarios. The humor is derived from the over-the-top nature of the club's endeavors, the exaggerated personalities of the characters, and the sheer absurdity of their attempts to achieve the impossible.

Throughout the series, the Jitensha Jozu Club's antics serve as a vehicle for exploring themes of friendship, perseverance, and the importance of pursuing one's passions, no matter how unconventional they may be. The series maintains a lighthearted and comedic tone, with a focus on delivering laughs through its absurd premise and eccentric characters. The narrative does not delve deeply into serious or dramatic elements, instead prioritizing humor and entertainment.