"Kodomo no Jikan: Kodomo no Natsu Jikan" is a three-episode OVA series that serves as a continuation of the original "Kodomo no Jikan" anime. The story revolves around Rin Kokonoe, a precocious and emotionally complex third-grade student, and her relationship with her homeroom teacher, Aoki Daisuke. Rin harbors deep feelings for Aoki, often expressing them in ways that blur the boundaries between childish innocence and inappropriate behavior. Aoki, while initially uncomfortable with Rin's advances, gradually becomes more attuned to her emotional struggles and the reasons behind her actions.

The narrative delves into Rin's troubled home life, revealing her strained relationship with her neglectful and emotionally distant guardian, her aunt Reiji Kokonoe. Rin's behavior is shaped by her longing for attention and affection, which she seeks from Aoki as a substitute for the parental care she lacks. The story also explores the dynamics between Rin and her classmates, particularly her close friends Kuro Kagami and Mimi Usa, who provide both comedic relief and emotional support.

Throughout the OVA, Rin's interactions with Aoki become increasingly layered as she confronts her feelings and the challenges of her personal circumstances. Aoki, though often conflicted about his role in Rin's life, begins to understand the depth of her emotional needs and the importance of providing her with guidance and stability. The series balances moments of lighthearted humor with poignant explorations of themes such as loneliness, maturity, and the complexities of human relationships.

The OVA maintains a focus on character development, particularly in its portrayal of Rin's growth and Aoki's evolving perspective on his responsibilities as a teacher and mentor. While the series occasionally touches on controversial themes, it approaches them with a nuanced tone, emphasizing the emotional and psychological dimensions of its characters. The narrative concludes with an open-ended resolution, leaving room for interpretation regarding the future of Rin and Aoki's relationship.