昏き夜と倶に来たる Extended to 20 minutes+
One of the BGM from Imperial Flag 3. This time feel a litlle calm, and the guitar part before looping is not bad too.
Other Shironeko Project extended BGM:
https://www.youtube.com/playlist?list=PLJSFfiBIf4LDlQUpy154dNJiRqeVQaZA3