"Sexy Commando Gaiden: Sugoi yo!! Masaru-san" is a comedic anime series centered around Masaru Hananokōji, a high school student who practices an unconventional martial art called "Sexy Commando." This self-styled martial art involves bizarre and nonsensical techniques, such as pretending to be a crab or striking dramatic poses, which Masaru insists are effective in combat. Despite its absurdity, Masaru is deeply committed to his craft and often finds himself in ridiculous situations as he attempts to prove its legitimacy.

The series primarily takes place in a high school setting, where Masaru’s eccentric behavior and unwavering confidence in Sexy Commando frequently clash with the expectations of his peers and teachers. His antics often lead to chaotic and humorous encounters, as he challenges others to duels or attempts to recruit new members for his martial art. Masaru’s best friend, Aoyama, serves as a grounded counterpart, often questioning Masaru’s methods but remaining loyal despite the constant embarrassment.

Throughout the series, Masaru faces various opponents, including rival martial artists, school bullies, and even teachers, all of whom are baffled by his unorthodox approach. Despite the lack of any real combat effectiveness, Masaru’s sheer determination and unpredictability often lead to unexpected outcomes, further fueling the comedic tone of the series. The narrative is episodic, with each episode presenting new challenges or scenarios that highlight Masaru’s peculiar personality and the absurdity of Sexy Commando.

The humor in the series derives from the stark contrast between Masaru’s unwavering belief in his martial art and the utter ridiculousness of his techniques. The supporting characters, including classmates and school staff, react with a mix of confusion, exasperation, and occasional admiration, adding to the comedic dynamic. While the series does not follow a continuous overarching plot, it maintains a consistent focus on Masaru’s antics and his interactions with those around him, creating a lighthearted and entertaining viewing experience.