"Shakugan no Shana-tan Returns" is a comedic spin-off of the main "Shakugan no Shana" series, presented in a chibi-style format. The narrative revolves around Shana-tan, a miniature, exaggeratedly cute version of the original protagonist Shana, who serves as a Flame Haze tasked with protecting the balance between the human world and the Crimson Realm. The series parodies the serious tone of the original, focusing on humorous, slice-of-life scenarios involving Shana-tan and other characters from the main series, reimagined in a similarly chibi-fied style.

The plot is episodic, with each segment featuring Shana-tan and her companions engaging in absurd, lighthearted situations. Key characters include Shana-tan, who retains her fiery personality but is often portrayed as overly dramatic or comically inept; Yuuji-tan, a diminutive version of Yuji Sakai, who frequently finds himself caught in Shana-tan's antics; and Alastor-tan, a tiny, mischievous version of the powerful being Alastor, who often provides sarcastic commentary. Other characters, such as Wilhelmina-tan and Margery-tan, also appear, contributing to the chaotic and humorous tone.

The series does not follow a continuous storyline but instead offers standalone comedic sketches. These sketches often parody events or themes from the main series, such as battles between Flame Hazes and Denizens, but with a focus on slapstick humor and exaggerated reactions. The interactions between characters are driven by their chibi-fied personalities, with Shana-tan's fiery determination and Yuuji-tan's exasperation serving as recurring sources of comedy. The series maintains a lighthearted tone throughout, appealing to fans of the original series while offering a fresh, comedic perspective on its characters and world.