"Dangerous Jii-san Ja" centers on a seemingly ordinary elderly man, Jii-san, whose unassuming appearance belies his extraordinary and often chaotic abilities. The series unfolds in a comedic and episodic format, with each episode presenting Jii-san in various absurd and unpredictable situations. Despite his age, Jii-san possesses superhuman strength, agility, and a knack for inadvertently causing mayhem wherever he goes. His actions frequently disrupt the lives of those around him, including his long-suffering family and neighbors, who struggle to cope with his antics.

The narrative explores Jii-san's interactions with a colorful cast of characters, including his exasperated but caring wife, his ambitious yet easily flustered son, and a group of quirky townspeople who often find themselves caught up in his misadventures. The series balances slapstick humor with moments of heartfelt connection, as Jii-san's actions, though disruptive, often stem from a genuine desire to help others or protect his loved ones. However, his methods are invariably unconventional and lead to unintended consequences.

Themes of family, aging, and the clash between tradition and modernity are woven into the story, as Jii-san's old-fashioned values and eccentric behavior frequently collide with the fast-paced, technology-driven world around him. Despite the chaos he creates, Jii-san's underlying kindness and resilience make him a beloved figure in his community, even as they brace themselves for his next unpredictable escapade. The series thrives on its blend of humor, action, and occasional moments of poignancy, offering a lighthearted yet engaging portrayal of an unconventional hero.