"Softenni!" is a sports-themed comedy anime centered around the lives of a group of high school girls who join their school's soft tennis club. The series is set at the fictional Aoi Middle School and primarily focuses on the daily antics and misadventures of the club members as they navigate both their sport and school life. Soft tennis, a variation of traditional tennis played with softer balls and lighter rackets, serves as the backdrop for the series, though the emphasis is more on humor and character interactions than on intense sports competition.

The main protagonist is Asuna Harukaze, a cheerful and energetic first-year student who joins the soft tennis club alongside her childhood friend, Chitose Nakajima. Asuna is portrayed as somewhat clumsy but highly enthusiastic, often bringing a lively dynamic to the group. Chitose, on the other hand, is more reserved and pragmatic, frequently acting as the voice of reason amidst the club's chaotic activities. The club also includes Kurusu Tachibana, a third-year student and the club's captain, who is known for her calm demeanor and occasional eccentricities. Rounding out the core group is Kotone Sakuragi, a second-year student with a sharp tongue and a competitive streak, and Yuuki Yamano, a first-year who is initially shy but gradually becomes more confident through her involvement in the club.

The narrative unfolds through a series of episodic vignettes that blend slice-of-life humor with lighthearted sports elements. The girls engage in various comedic situations, ranging from quirky training sessions and clubroom shenanigans to interactions with rival teams and school events. While the soft tennis matches are a recurring feature, the series often prioritizes the characters' personalities and relationships over the technical aspects of the sport. The humor is largely derived from the exaggerated and absurd situations the characters find themselves in, as well as their distinct quirks and interactions.

Throughout the series, the club members face challenges both on and off the court, such as preparing for tournaments, dealing with rival teams, and balancing their academic responsibilities. However, the tone remains light and comedic, with minimal dramatic tension. The focus is on the camaraderie and growth of the characters as they bond over their shared experiences in the club. The series also occasionally incorporates parodic elements, poking fun at common tropes found in sports anime and school-life genres.

"Softenni!" does not delve deeply into complex character development or intricate plotlines, instead opting for a straightforward and entertaining approach. The characters' personalities and relationships drive the narrative, with each episode offering a self-contained story that contributes to the overall lighthearted atmosphere. The series concludes without a definitive resolution, maintaining its episodic structure and leaving the characters' futures open-ended. Overall, "Softenni!" is a comedic and character-driven series that uses soft tennis as a vehicle for humor and slice-of-life storytelling.