Pochirou is the deuteragonist and faithful companion to fifth-grade elementary student Eiji Toomatsu. Identified as a dog, Pochirou acts as Eiji's "inspiration" buddy during their invention activities. The pair's central adventure begins upon discovering the mysterious "Pikachin Research Book," detailing the seven tools of the Pikachin Kit. After Eiji presses a button inside the book, the kit arrives via a "Future Amazon" delivery. Pochirou actively participates alongside Eiji in assembling these tools using provided blueprints, though each initial assembly consistently remains 99% complete. This character directly embodies the franchise's core concept: "Pikachin" signifies the spark of inspiration for new inventions, visually represented by a lightbulb illuminating above one's head. The framework defines invention as "99% plastic models, 1% inspiration," with Pochirou supporting the crucial ideation phase.

Merchandise explicitly refers to Pochirou as a "robo-dog." The character was included in a discontinued plastic model set featuring the Pikachin Encyclopedia, reinforcing the link to model assembly and invention central to the series. This set contained a small plastic Pochirou figure, tools, and decorative stickers.

No concrete information exists regarding Pochirou's origins, specific personality traits, physical appearance beyond being a dog, or character development across any narrative media. Available material focuses solely on Pochirou's functional role within the invention-focused premise alongside Eiji, without elaboration on background stories or narrative progression.