"Mattaku Saikin no Tantei Tokitara" is a mystery-comedy anime that revolves around the peculiar partnership between Toki, a high school student, and Tantei, a self-proclaimed detective who appears in the form of a small, anthropomorphic creature. The series is structured as a collection of episodic cases, each presenting a unique mystery that the duo must solve together. Toki, initially skeptical of Tantei's abilities, gradually becomes entangled in a series of bizarre and often humorous investigations.

The narrative begins when Toki encounters Tantei, who claims to be a detective capable of solving any mystery. Despite Tantei's diminutive size and eccentric demeanor, the creature demonstrates a surprising knack for unraveling complex puzzles. Toki, though reluctant at first, is drawn into Tantei's world as the two tackle a variety of cases, ranging from mundane school-related incidents to more elaborate and supernatural occurrences. Each episode typically follows a formula where Tantei employs unconventional methods to uncover the truth, often leading to unexpected and comedic outcomes.

The dynamic between Toki and Tantei forms the core of the series. Toki serves as the grounded, rational counterpart to Tantei's flamboyant and often absurd antics. While Toki frequently questions Tantei's competence, the detective's unorthodox approach consistently proves effective, albeit in ways that defy logic. The interplay between the two characters drives both the humor and the progression of the mysteries, creating a balance between lighthearted comedy and engaging problem-solving.

Supporting characters, including Toki's classmates and other individuals they encounter during their investigations, add depth to the narrative. These characters often play key roles in the cases, either as suspects, witnesses, or individuals seeking the duo's help. The episodic nature of the series allows for a diverse array of scenarios, ensuring that each mystery feels fresh and distinct.

Thematically, the series explores the nature of truth and the often unpredictable ways in which it can be uncovered. While the tone is predominantly comedic, there are moments of genuine intrigue and clever deduction that highlight the detective genre's traditional elements. The juxtaposition of Tantei's outlandish methods with Toki's skepticism creates a unique blend of humor and mystery, making the series accessible to a wide audience.

Overall, "Mattaku Saikin no Tantei Tokitara" offers a lighthearted yet engaging take on the detective genre, combining quirky characters, inventive mysteries, and a consistent undercurrent of humor. The episodic structure ensures a steady pace, while the evolving relationship between Toki and Tantei provides a narrative thread that ties the series together.