And I'll do a two-for today, since it's the first day.
Hitoto Yo - Morai-naki
Released as her debut single in 2002, Morai-Naki made her an instant star. I remember hearing this song and being so taken with her voice - there are parts of it that are so J-POP, but also a polish and beauty that is unique in its own right. She beautifully melds pop music with an enka-ish undertone. Her whole debut album was a breath of fresh air, though I admit I kind of fell off board with her with subsequent albums.