I'm not a skier by any means. I had my one and only try at downhill skiing with my junior high school students way back in 1990....was on the slopes for the entirety of an hour before I slunk back to the lodge for several more hours of cocoa and reflection by the frost-tinged windows. Anyways, my thoughts whenever I hear "Koibito ga Santa Claus" usually bring forth images of a Santa Claus manning not a sleigh but a starship driven by eight warp engines named Donner, Dancer, etc. The arrangement has that pop/rock feeling of good times at Christmas, which is basically what the Yuletide is all about in Japan: pop those firecrackers, clink that Beaujolais Nouveau, lunge into that Kentucky Fried Chicken!
"Koibito ga Santa Claus" was never released as an official single but was part of Yumi Matsutoya's 10th album, "Surf & Snow" released in December 1980. The album got as high as No. 7 on Oricon. In Yuming's huge repertoire, this song is probably up in the Top 10 in popularity.