Akikan!

あらすじ

One summer day, high school student Kakeru Daichi buys a can of melon soda from a vending machine, which unexpectedly transforms into a girl he names Melon. She is an "Akikan," or "empty can," and other Akikan girls soon appear. Akikan girls require carbon dioxide to survive, which they obtain through kissing. A government official informs Kakeru and Melon about the "Akikan Elect," a battle between steel and aluminum cans that Melon must participate in. Initially hesitant, Melon is persuaded to fight after encountering a rival can.