"Yuube no Himitsu" was Ogawa's debut single from February 1968, and was written by Ichiko Tama（タマイチコ） and composed by Maria Chiba（千葉マリア）who was only 18 years of age at the time. Ogawa herself had just turned 19 when she started out as a 60s aidoru. It was quite the difference back then as to how an aidoru sounded back then compared to how an aidoru sounded in the 80s and now in the 21st century, wasn't it?
Here she is on a 1995 NHK program singing "Yuube no Himitsu". Hearing the original version, I was surprised at how mature she sounded considering her age although her vocals didn't sound as if she had been this jaded seen-it-all, heard-it-all woman. There was still this innocence about her delivery of the lyrics which had her plaintively begging her paramour not to reveal anything about the night before so that the experience could stay pristine. For me, the Latin rhythm brings to mind a romantic couple tripping the light fantastic on the dance floor, and there's even a bit of a feeling in my weird imagination that this could have fit onto the soundtrack of a James Bond film...notably "You Only Live Twice" but that had already been out the previous year.
Another interesting point about the song involved the recording. Ogawa had been suffering from a fever at that time, so her voice went somewhat whispery when she was behind the mike. That obviously didn't hurt the record at all, and it was probably because of that fever's effects that had the male listeners swooning. She also ended up appearing on the Kohaku Utagassen for 3 years in a row with her debut starting things off.
"Yuube no Himitsu" reached No. 1 on Oricon. However, Japan wasn't the only place to have applauded the song's charms. During the early 70s, it apparently (for reasons which have yet to be cleared up, according to the J-Wiki article on Ogawa) made the trip over to South America under the title of "Amor Japones" and become a hit over there as well. The strange thing is that although it was still Ogawa's voice, the singer's name was given as Akaina Akomoto.