I heard this on one of the two Hiromi-chan cassette tapes that Mom got me when she and Dad came back from vacation in Japan in the mid-80s. It was a BEST compilation with all her songs dating up to 1984, and all of her earliest material just happened to wrap Side B. So I got to hear "Romance" and then "Sentimental" which is a bit more whimsical-sounding than the former song. Depending on my mood, I've often it liked it better than "Romance" .
One piece of trivia I gleaned from the J-Wiki article for the song is that the original title was supposed to have been "Kanshouteki na Juu-nana Sai"（感傷的な17才...Sentimental 17）. However on the advice of a fortune teller called Shinjuku-no-Haha（新宿の母...Shinjuku Mama）, the title was changed to its katakana version of the English word since Iwasaki was told that her first three songs should have katakana titles. Thus, Singles 1-3 were "Duet", "Romance" and "Sentimental". But I guess she, the songwriters and everyone else on the staff decided to play things even more safely and dubbed the 4th single into katakana as well: "Fantasy"（ファンタジー）. I gather that it is not just athletes who are superstitious celebs.