The unforgettable 1983 Christmas classic (though this video is a bit cornball).
This song also became the theme for the Japan Railway (JR) “Christmas Express” CMs for the bullet train (1988-1992), one of the most romantic CM campaigns ever, compiled here:
This is the English version of the song. A bit lost in translation, but it’s still good:
Addendum: I just noticed a detail in the first JR CM. You can see the breath/steam of the boyfriend hiding behind the station platform pillar at 0:18-0:19, before he appears to surprise his girlfriend. Nice touch!