Prayers from an Ancient Sky

Prayers from an Ancient Sky (古き空より祈りをこめて) was a story event in Assault Lily: Last Bullet, starring Sasaki Ran and Ando Tazusa. It ran from August 11, 2021 to August 31, 2021, and was rerun in September 2022.

Translation
There is a full set of subtitled YouTube videos by GEHENA Subtitle Labs.