"Ninja Nonsense" is a comedic anime series that revolves around the absurd and chaotic daily life of Shinobu, a young ninja-in-training, and her eccentric mentor, Onsokumaru. Set in a fictional ninja village, the story blends slapstick humor, surreal situations, and parodies of traditional ninja tropes. Shinobu, despite her dedication to mastering ninja skills, often finds herself entangled in bizarre and nonsensical scenarios, largely due to Onsokumaru's unpredictable and mischievous behavior. Onsokumaru, a self-proclaimed "super ninja," is a floating, spherical creature with a penchant for causing trouble, often leading Shinobu into embarrassing or ridiculous predicaments.

The series also introduces Kaede, Shinobu's classmate and best friend, who becomes an unwitting participant in the chaos. Kaede is a normal high school student with no connection to the ninja world, but her life takes a turn when she discovers Shinobu's secret ninja identity. Despite her initial confusion, Kaede adapts to the absurdity and often finds herself dragged into Shinobu and Onsokumaru's antics. The dynamic between the three characters forms the core of the series, with their interactions driving much of the humor.

Episodic in nature, "Ninja Nonsense" features self-contained stories that highlight the characters' quirks and the absurdity of their world. Common themes include Shinobu's attempts to prove her ninja prowess, Onsokumaru's schemes to embarrass or outwit her, and Kaede's struggle to maintain a semblance of normalcy. The series frequently employs exaggerated physical comedy, fourth-wall breaks, and parodies of anime and ninja clichés, creating a lighthearted and irreverent tone.

The narrative does not follow a linear plot but instead focuses on the characters' interactions and the escalating absurdity of their situations. While Shinobu strives to be a competent ninja, her efforts are often undermined by Onsokumaru's antics or her own lack of experience. Kaede serves as a grounding presence, providing a relatable perspective amidst the chaos. The series balances its humor with moments of camaraderie, showcasing the unlikely friendship between Shinobu and Kaede despite their vastly different backgrounds.

Overall, "Ninja Nonsense" is a comedic exploration of ninja culture through a lens of parody and absurdity, with its humor derived from the exaggerated personalities of its characters and the unpredictable nature of their adventures. The series thrives on its ability to subvert expectations and deliver over-the-top comedic scenarios, making it a distinctive entry in the genre of ninja-themed anime.