"Kero Kero Keroppi no Sanjūshi" is an anime series based on the beloved Sanrio character Keroppi, a cheerful frog. The narrative draws inspiration from Alexandre Dumas' classic novel "The Three Musketeers," reimagining the tale with Keroppi and his friends in the lead roles. The story is set in a whimsical, anthropomorphic world where Keroppi, alongside his companions Koroppi and Keroleen, embarks on a swashbuckling adventure filled with camaraderie, bravery, and lighthearted humor.

Keroppi takes on the role of a young, aspiring musketeer, embodying the spirit of D'Artagnan from the original story. His journey begins when he leaves his hometown to join the ranks of the royal musketeers, a group of elite protectors serving the kingdom. Along the way, he encounters Koroppi and Keroleen, who become his loyal companions. Together, the trio faces various challenges, including thwarting the schemes of antagonists who threaten the kingdom's peace. The series balances action with moments of friendship and moral lessons, emphasizing themes of loyalty, courage, and teamwork.

The antagonists, often portrayed as bumbling yet persistent, provide comedic relief while posing obstacles for the protagonists. Their plans typically involve attempts to undermine the musketeers or disrupt the kingdom's harmony, but Keroppi and his friends consistently outwit them through clever strategies and unwavering determination. The episodic structure of the series allows for a variety of adventures, each highlighting the characters' growth and their commitment to upholding justice.

The main characters are characterized by their distinct personalities and roles within the group. Keroppi, as the optimistic and determined leader, drives the narrative forward with his enthusiasm and sense of duty. Koroppi, often depicted as more cautious and thoughtful, serves as a grounding force, while Keroleen brings a spirited and resourceful energy to the trio. Their dynamic interactions and shared goals form the emotional core of the series, making it accessible and engaging for younger audiences.

The setting is a vibrant, fantastical world that blends elements of medieval Europe with the playful aesthetic of Sanrio's universe. The animation style reflects the lighthearted tone of the series, with bright colors and expressive character designs that enhance the storytelling. While the series primarily targets a younger demographic, its timeless themes and charming execution have garnered a broader appeal among fans of Sanrio's characters and classic adventure tales.