Another part of the Masahiko Kondo （近藤真彦）juggernaut from 1981. Released in September, just after "Blue Jeans Memory", "Gingiragin ni Sarigenaku"(Cheerfully [?] Nonchalant) had a brief dogfight with Seiko Matsuda's（松田聖子）"Kaze Tachinu"（風立ちぬ） but held onto the top spot for a total of 6 weeks. Furthermore, it got Matchy a Japan Record Award for Best Newcomer, and a spot on the 1981 Kohaku Utagassen. Ultimately, it not only was the 21st-ranked song of the year, but even at the end of 1982, it was ranked 37th.
One of the fellows on YouTube remarked that it was Japanese disco music, and yes, there seems to be a bit of Rod Stewart's "Do Ya Think I'm Sexy?"-era music in the arrangements. However, I think the adjective for Matchy during his performances of the song in concert or on the TV ranking shows would've been "cute" .
To be honest, I've heard the karaoke version more often than the version sung by Matchy himself. "Gingiragin ni Sarigenaku" was a popular request at Kuri, and the video was hilarious. It featured what looked like a topless model from Abercrombie & Fitch just boogeying around outside. Hoped it paid well, pal. I wanted to find the video on YouTube, but alas the karaoke videos of the song there are much more subdued.
The composer of the song? Kyohei Tsutsumi（筒美京平）, who had created Saori Minami's（南沙織） "Juu-nana Sai"（１７才...17 Years Old) and Miki Hirayama's（平山みき）"Manatsu no Dekigoto"（真夏の出来事....A Midsummer Happening）a decade earlier. As for the lyricist, it was Ayumi Date（伊達歩）, a pen name for author Shizuka Ijuuin（伊集院静）.