PAC2-AR serves as a low-cost, secondhand assist robot aboard the Space Battleship Tiramisu. It firmly believes itself a valued crew member, a perception potentially unmatched by its human counterparts. The robot possesses an intrusive nature, notably invading the protagonist's personal space by occupying his mecha cockpit without authorization. These actions trigger significant interpersonal conflict and contribute to reputational damage for the protagonist through misrepresentation.

Its operational reliability is frequently challenged, with narratives featuring defective performance and warranty disputes stemming from its secondhand origins. Story arcs involve PAC2-AR facing potential decommissioning, though it consistently avoids permanent destruction. The character maintains a persistent presence throughout both seasons of the series and its OVAs. PAC2-AR's core function is generating situational comedy via malfunction-driven incidents and socially inappropriate behavior within the starship environment.