Kyosuke Kosaka, an average high school student, lives a relatively ordinary life until he discovers a hidden side of his younger sister, Kirino. Kirino, who is popular, academically successful, and athletic, secretly harbors an obsession with eroge (erotic games) and anime, particularly those featuring little sister characters. This revelation comes when Kyosuke stumbles upon one of her games, leading to an awkward confrontation. Despite their previously distant relationship, Kirino reluctantly confides in Kyosuke and asks for his help in keeping her hobby a secret while also seeking his advice on navigating the otaku subculture.

As the story progresses, Kyosuke becomes more involved in Kirino’s world, accompanying her to otaku events, meeting her like-minded friends, and even helping her create her own doujinshi (self-published works). Among these friends is Kuroneko, a sharp-tongued and intelligent girl who shares Kirino’s interests but often clashes with her due to their differing personalities. Another key figure is Saori, a kind and knowledgeable otaku who acts as a mentor figure to Kirino and Kyosuke. Through these interactions, Kyosuke begins to understand Kirino’s passion and the challenges she faces in balancing her public persona with her private interests.

The narrative explores themes of sibling relationships, societal expectations, and the stigma surrounding otaku culture. Kirino’s struggle to reconcile her dual identities forms the emotional core of the story, while Kyosuke’s growing support for her highlights the evolving dynamics of their relationship. The series also delves into the broader otaku community, portraying its complexities and the camaraderie among its members.

As the story unfolds, Kirino’s ambitions extend beyond her hobby, leading her to pursue a modeling career and later a move to the United States to further her education. These developments create tension and emotional moments as the siblings grapple with their feelings and the prospect of separation. The series concludes with a focus on their bond, emphasizing the growth they’ve experienced together and the mutual understanding they’ve achieved.

Throughout the manga, the characters’ interactions are marked by humor, conflict, and heartfelt moments, creating a balanced narrative that blends comedy with emotional depth. The exploration of otaku culture, combined with the central sibling relationship, makes the story both relatable and unique within its genre.