Was just watching a Kagerou Project retrospective and realized Star-Mine was probably written at the height of its downfall when they had to cancel the sequel due to all the copyright fuckery (2021 to 2022). Umes VA iirc even said it's one of the first songs they recorded. It definitely wasn't part of the Kagerou Project lineup but it was still probably written back in that same mindset.

Definitely gives the song a more nuanced taste to it. It's kinda of like Endless Dance where they may have approached the guy from Keynote back before he broke up with them.