Trying to categorize this article for today, I can only remark that this song has kinda popped out of the second-string tier of aidoru from the 70s and 80s who came and went with the wind. But the trio who sang "You Are Sexy", Fever（フィーバー）, has actually popped up on this blog once before and that would be the article that nikala had written up a couple of years ago in 2014 about her favourite techno kayo songs.
However, Fever's 2nd single "You Are Sexy" from August 1979 was far from the blips and bleeps of a synthesizer. The melody by Yusuki Hoguchi（穂口雄右）most certainly put it in the annals of good ol' disco. I mean, looking at the trio above in their hot pants and listening to the song, I think they answered the question "What if Candies and Pink Lady had been merged with not-as-good choreography?". Chinfa Kan（康珍化）, who would come up with lyrics for many an Anri（杏里）tune in the next decade, provided the words for "You Are Sexy".
As a B-kyu aidoru group, there isn't a whole heck I could find in terms of information on Fever, and a good chunk of that has already been provided in nikala's paragraph on them. Just 4 singles and 1 album before the Fever broke (up) in late 1980.