Long time, no hear. "Itsuka Kitto" (Someday For Sure) was Misato Watanabe's（渡辺美里）25th single from February 1993. I'm not sure where I first heard it...it could have been on one of her BEST compilations or perhaps I may have even heard it at that lone Misato concert I attended with my friends back in 1995 in Yokohama.
It doesn't quite reach the heights of some of her big hits like "My Revolution" or "Summertime Blues" but it's still a nice enough tune. And although Misato's lyrics talk about that unrequited love as winter turns into spring, the melody and arrangement by Yasushi Ishii（石井妥師）make it sound just about Xmas-y, and that video below of her performing the song at what looks like some winter festival pretty much seals the deal on my theory. Plus, her vocals also come across like the voice of an encouraging angel.
"Itsuka Kitto" made it to No. 7 on Oricon. It was also a track on her 8th album from July 1993, "Big Wave" which hit No. 1 and was the 18th-ranked album of the year.