Kakeru Daichi, a sixteen-year-old Kyuugetsu Academy student, obsessively collects rare juice cans and peppers conversations with lewd humor. His mundane routine shatters upon acquiring a melon soda can that morphs into Melon, a humanoid Akikan engineered for combat in a government experiment pitting steel against aluminum cans. Traumatized by a junior high incident where he violently rescued childhood friend Najimi Tenkuji from kidnappers—an act that drew public backlash and forced his relocation—he resists conflict. Yet the "Akikan Elect" initiative drags him into battles between anthropomorphized cans.

Reluctance gives way to rebellion as Kakeru allies with fellow dissenters to dismantle the project. He safeguards not only Melon but also Shiruko, a timid steel Akikan born from sweet red bean soup, assuming responsibility for her safety. His relationships teem with friction: Melon’s tsundere outbursts clash with his flirtatious antics, while Najimi’s unreciprocated feelings fuel ongoing tension.

Strategic ingenuity emerges as Kakeru confronts adversaries like Hidehiko Otoya, the project’s overseer, whose predatory behavior—including non-consensual OVA encounters—underscores Kakeru’s fragility amid growing resolve. Ethical boundaries define his choices, rejecting manipulative tactics like exploiting Najimi’s drunkenness and defying authority to shield Akikans.

His arc traces a shift from detached collector to defiant leader, mediating alliances with Akikans such as Yell, an aluminum-can combatant, and Miku, an assimilator. The narrative weaves absurdist humor with darker threads of trauma and exploitation, framing Kakeru’s evolution as a reckoning with systemic cruelty and his own fractured past.