From Anime News Network:
Eri Kawai, the singer-songwriter for Aria, Utawarerumono, and several other anime and live-action series, passed away on Monday at 11:40 a.m. in Japan.

[...]

Kawai had been in medical treatment since earlier this year and had to cancel a July 10 solo performance in Tokyo as a result. A wake will be held on Wednesday, and the funeral service will be held on Thursday.

[Also on her website, for those who can moonspeak]

I first heard of her name from the beautiful Madoromi no Rinne, the ED song of Utawarerumono. After that, I began to wonder if Eri Kawai was in any way related to the talented composer Kenji Kawai. I didn’t notice that she has also worked in various other songs for several anime, some of which I have even watched myself, such as Sketchbook and Bamboo Blade.

I didn’t get to hear much else of her works, but I feel that her passing is a great loss to the anime industry. She produces beautiful music and I would have definitely loved to hear more of her. My heart goes out to her family and her fans in Japan :(

May you find peace and happiness in a better place.