Basically the human girl(the real Akari) at the end wonders why the mannequin(the main character Akari) looks exactly like her, while her friend explains that maybe it's because she once did jobs as a seifuku model, so the designer of the mannequins took her likeliness. And that this museum from the Showa period was a place where lewd mannequins were displayed but was closed down recently due to the town's objections.
In the end this whole series was all a mannequin's dream...