"Kin-iro Mosaic: Pretty Days" is an anime OVA that serves as a continuation of the "Kin-iro Mosaic" series, also known as "Kiniro Mosaic" or "KINMOZA!" in some regions. The story revolves around the daily lives and interactions of a group of high school girls, blending slice-of-life elements with lighthearted comedy. The central characters include Shinobu Omiya, a Japanese girl with a deep fascination for British culture, and Alice Cartelet, a British girl who moves to Japan to live with Shinobu and experience Japanese culture. Their friendship forms the core of the narrative, with their contrasting personalities and cultural backgrounds providing much of the humor and charm.

The OVA is structured into three distinct segments, each focusing on different moments in the characters' lives. The first segment explores a summer festival, where the group enjoys traditional Japanese activities such as wearing yukata, playing games, and watching fireworks. The second segment shifts to a school cultural festival, showcasing the girls' efforts to organize a café and participate in various events. The final segment takes place during winter, highlighting a Christmas party and the warmth of their friendships as they exchange gifts and celebrate together. Throughout these vignettes, the interactions between Shinobu, Alice, and their friends—Aya Komichi, Yoko Inokuma, and Karen Kujo—are depicted with a focus on their camaraderie and the small, meaningful moments that define their relationships.

The narrative maintains a light, episodic tone, emphasizing the everyday joys and challenges of adolescence. The characters' personalities are central to the story: Shinobu's enthusiasm for British culture contrasts with Alice's initial struggles to adapt to Japan, while Aya's cheerful demeanor, Yoko's tomboyish nature, and Karen's playful teasing add depth to the group dynamic. The OVA does not introduce significant plot developments or conflicts but instead reinforces the themes of friendship, cultural exchange, and the simple pleasures of life. It serves as a nostalgic and heartwarming addition to the series, appealing to fans of the original show while maintaining its accessible, slice-of-life charm.