I'm not sure I can really describe why I love Kajiura-sensei's music, but I can try
The first song I heard was fairytale by Kalafina, and it literally gave me chills! I fell in love with their voices and I had to hear more. I bought Seventh Heaven, listened to it all and loved most of the songs (if not all of them) but I didn't really wonder why they were so gorgeous! But after a while I started listening to more of Kajiura-sensei's music, and I realized that the beauty wasn't restricted to Kalafina songs.
Anyway, the more I listened to Kajiura-sensei's music, the more I found wonderful songs. I think the reason why I fall in love with them, whether the song is Salva Nos, or Mizu no Akashi, or even just Innocent Days, that sweet little piano piece from Rekishi Hiwa Historia, is that there is a huge amount of
emotion in every piece. Salva Nos is filled with passion and movement - Mizu no Akashi has sadness and hope - and Innocent Days gives you an intangible bittersweet feeling. Even though Kajiura-sensei may use some similar arrangements and chord patterns (if that's the right term) at times, the emotion in her music is so intense and focused that I can't help but love almost every piece of hers I hear. When I saw her playing the piano live, I realized that she truly loves music, and that she puts that feeling into every note of music she makes, no matter what. She spoke to my heart right away, from the first strains of fairytale, and I think that's the reason why I love her music.
Sorry if I was a little dramatic