"Tantei Opera Milky Holmes Dai-Ni-Maku" is the second season of the "Tantei Opera Milky Holmes" series, continuing the adventures of the Milky Holmes detective team. The story revolves around four young girls—Sherlock Sherringford, Nero Yuzurizaki, Elly Cunningham, and Cordelia Glauca—who attend the Holmes Detective Academy. Each possesses a unique ability known as "Toys," supernatural powers essential for solving mysteries. However, in the first season, they lost their Toys due to a confrontation with the thief group Arsène.

In this season, the Milky Holmes team struggles to regain their lost abilities while continuing their detective work. The narrative explores their daily lives at the academy, their interactions with classmates, and their ongoing rivalry with the Arsène group. The Arsène members, led by the enigmatic Twenty, remain a persistent threat, often challenging the girls with elaborate heists and schemes. Despite their lack of Toys, the Milky Holmes team relies on their wit, teamwork, and determination to tackle these challenges.

The series balances comedic and lighthearted moments with occasional dramatic undertones. The characters' personalities are further developed, with Sherlock's cheerful optimism, Nero's tsundere tendencies, Elly's eccentricity, and Cordelia's calm demeanor playing key roles in their dynamic. Supporting characters, such as the strict but caring teacher Henriette and the rival detective group G4, add depth to the story. The episodic structure allows for a mix of standalone mysteries and overarching plotlines, culminating in a climactic confrontation with the Arsène group.

Themes of perseverance, friendship, and self-discovery are central to the narrative. The Milky Holmes team's journey to reclaim their Toys serves as a metaphor for overcoming personal setbacks and growing stronger through adversity. The series maintains a playful tone, often parodying detective tropes while paying homage to classic mystery literature. Overall, "Tantei Opera Milky Holmes Dai-Ni-Maku" builds on the foundation of its predecessor, offering a blend of humor, mystery, and character-driven storytelling.