Dr. Leonardo invented Tondekeman, a sentient kettle-shaped time machine capable of creating dimensional portals. His laboratory hosts the opening incident where protagonists Hayato and Yumi accidentally activate this device, displacing them to ancient Baghdad.

His background is dramatically unveiled in the series' conclusion: he reveals himself as the historical polymath Leonardo da Vinci. This connection accounts for his extraordinary technological prowess and ability to create machinery centuries ahead of its time.

He appears primarily at critical narrative points: initiating the protagonists' journey through the accidental activation and later contextualizing the time travel events via his historical identity. His laboratory houses unexplained inventions beyond Tondekeman, though their functions remain unexplored.

His role culminates when he clarifies Tondekeman's origins and purpose, directly linking the series' time travel mechanics to his Renaissance-era ingenuity. This revelation reframes his earlier actions as part of his lifelong pursuit of scientific innovation.