Kaori Kishitani / 岸谷香 – レクイエム
10th song on Kaori Kishitani Album “Piece of Bright”
Full single is available on Ototoy, but you need a vpn if you live outside Japan:
https://ototoy.jp/_/default/p/894172
Keiichi Tomita worked on the 6th and 10th songs on this album.