"+Tic Elder Sister" is a comedic manga series that revolves around the daily life of Itsuki Iba, a high school student who becomes the target of his older sister Chihiro's eccentric and over-the-top affections. Chihiro, a college student, is obsessed with her younger brother to an extreme degree, often engaging in exaggerated and absurd antics to express her love for him. Her behavior ranges from playful teasing to outright bizarre actions, such as dressing up in elaborate costumes or creating elaborate schemes to spend time with Itsuki. Despite her overbearing nature, Chihiro's actions are portrayed in a humorous light, emphasizing the comedic tone of the series.

Itsuki, on the other hand, is a more grounded character who often finds himself exasperated by his sister's antics. While he cares for Chihiro, he frequently struggles to maintain a sense of normalcy in his life as her antics disrupt his daily routine. The dynamic between the siblings forms the core of the story, with Chihiro's relentless pursuit of her brother's attention serving as the primary source of comedy. Supporting characters, such as Itsuki's classmates and other family members, occasionally appear to add variety to the narrative, but the focus remains firmly on the sibling relationship.

The plot is episodic, with each chapter presenting a new scenario in which Chihiro's over-the-top behavior creates chaos for Itsuki. The humor often stems from the contrast between Chihiro's exaggerated actions and Itsuki's more reserved reactions, as well as the absurdity of the situations they find themselves in. While the series does not delve deeply into dramatic or emotional themes, it occasionally touches on the underlying bond between the siblings, hinting at a genuine affection beneath Chihiro's eccentric exterior.

Overall, "+Tic Elder Sister" is a lighthearted and comedic exploration of sibling relationships, characterized by its exaggerated humor and focus on the antics of its central characters. The series thrives on its ability to balance absurdity with moments of genuine connection, making it an entertaining read for fans of comedy manga.