I'd say around winter of 2004. I had been into Utada Hikaru for only a little while, and I was reading reviews of her albums, and I saw somebody make a comparison to her and Ayu. I decided to check it out, and the first song I downloaded was "Catcher in the Light". From then on, I downloaded her MY STORY album, which had coincidentally just came out, and I was hooked. I absolutely loved it. I downloaded the rest of her discography, and now here I am.
Since then, I've purchased all of her albums, and even a few singles.