High schooler Kakeru Daichi buys a melon soda from a vending machine, and the can turns into an aloof, attractive girl he names Melon, one of several sentient 'Akikan,' or empty cans, that start appearing around him. The cans need carbon dioxide from kissing to hold their human form, and Kakeru is pulled into the state-run contest that pits aluminium Akikan against steel ones to settle which kind of can is superior.