During that graduation trip to Japan in 1981 as I was walking the streets of Tokyo and Osaka, I often saw these huge posters of these 3 teenage boys posing cute with the katakana underneath "Blue Jeans Memory".
The theme song, "Blue Jeans Memory" was sung by Kondo, or as he is known by fans, Matchy. It was his 3rd single and was a huge success. I remember a couple of my classmates from Japanese school playing the tape of the song over and over again when we all returned to Toronto. It hit No. 1 on the Oricon weeklies, and was the 11th-ranking single of 1981. In fact, Matchy's first four singles ended up in the Top 30 of the year (3rd, 11th, 20th and 21st), and all of them peaked at either 1 or 2 in the weeklies.
I may have categorized the song as "aidoru" but it comes off as an electric guitar-based rock fest. The fellow, tuberomeotap, who uploaded his video certainly thought so. There was also one line that left the biggest impression: "Sayonara nante...ienai yo....BAKAYARO!"（さよならなんて。。。言えないよ。。。バカヤロ！）"I can't say something like goodbye.....FxxK!" Well, I'm not sure if Matchy meant to be quite that profane....
Anyways, keep on rockin'.
September 15, 2020: Well, after nearly 40 years, I finally got to hear the soundtrack version of "Blue Jeans Memory" from the movie. It launches with a huge Prince-like rock riff before it slowly churns into the main song which is slightly stripped down, mostly in the lack of a background chorus although the familiar vocals of Matchy are still there. After we all returned from Japan in August 1981, most of us returned for one more year of Japanese Language School (we were gluttons for punishment), a couple of my classmates who had really gotten onto the Tanokin Trio bandwagon brought a tape deck and often played this version of the song during recess.