I wasn't quite sure what to make of "Atsuki Kokoro ni" (In A Passionate Heart) when I first heard it on "Sounds of Japan". It didn't quite sound like an enka song but it didn't really sound like a regular pop tune either. And this was the first that I had heard of Akira Kobayashi（小林旭）. But later on, I learned that he started his long career in Japanese showbiz as an actor for Nikkatsu Studios in 1956 and was placed alongside cinematic legend Yujiro Ishihara （石原裕次郎）as one of the young turks for the studio.
Looking at the J-Wiki article for Kobayashi, he also has a very long line of singles that started with "Onna wo Wasurero"（女を忘れろ...Forget Women）in 1958 and has continued up to 2013. However with a lot of folks, it's "Atsuki Kokoro ni" that is most associated with Kobayashi. As I said in the first paragraph, the song doesn't categorize easily. When I further listened to it, it sounded like something suited to a Hollywood western, and at the time I was still accustomed to knowing Japanese popular music as two distinct entities: pure enka and aidoru (well, there is also YMO...).
Much later, I found out that the song was composed by the late Eiichi Ohtaki （大瀧詠一）who seemed to specialize in crafting these heroic-sounding songs, such as "Saraba Siberia Tetsudo"（さらば、シベリア鉄道）and "Fuyu no Riviera"（冬のリビエラ）. Initially, Kobayashi was less-than-impressed when he had heard the demo tape for "Atsuki Kokoro ni" but when he heard about the string arrangement by Norio Maeda （前田憲夫）at the recording studio, he quickly changed his tune (no pun intended). And on hearing the grand introduction, he got the image of a John Wayne oater and concluded that perhaps he could take this song on (so, it wasn't just me then). As someone who spent years playing tough heroes, I can imagine how this would appeal to him. Lyrically, though, Ohtaki asked Yu Aku （阿久悠）to take the helm instead of his usual songwriting partner Takashi Matsumoto （松本隆）since Aku could bring a more traditional style to the words.
The song managed to get as high as No. 12 on the Oricon singles charts after its debut in November 1985 and later became the 20th-ranked song of 1986. It also became the winner of three prizes at the Japan Record Awards, including one for songwriting. Kobayashi also appeared on the 1986 Kohaku Utagassen to sing "Atsuki Kokoro ni", something that he repeated at the 1994 Kohaku.