It's basically the hentai take on "The Emperor's New Clothes" classic tale.
Sofia is the queen of the country, beloved by the citizens. She is reaching a certain age and so far, even though she has tried different methods, hasn't been lucky in providing an heir to her husband.
Then comes the rumor -extendend by himself- that there a dressmaker in town (Frodor, the fat guy with a moustache) capable of making magnificent clothes that are invisible only to idiots. His plan succeed and the queen calls him to palace to request a dress to help her seduce the husband.
Second chapter should be easy to follow. With the excuse of taking measures and because of course he "is wearing clothes", Frodor expend the night with Sofia. When the dress is presented to the king the next day he decides that such beauty should be shared with the common citizens...hence the public unveiling and group scene where no one is naked and having sex, of course.
The tale ends with Sofia improving her relations with her husband, the kingdom expecting an heir and the new clothes becoming the norm. Meanwhile, Frodor leaves in search of his next vict...clients.