Yeah, and that's mostly what it is, but the route I mentioned stands out from the rest. I've read all of Overdrive's other VNs, and this route is quite possibly the darkest thing they've written, even compared to Bokuten.
If anyone here wants to know what happens in the route without having to read it themselves, I can try doing a summary. There will be heavy spoilers, obviously.
I doubt this summary alone does it justice, since the writing and music are what truly gives this route its dark ambience. In any case, despite how depressing this part of the game may be, I still don't feel like marking the censored version of Musicus as "adult" is the right call, considering the fact that there are other games and VNs out there that were given a pass despite their disturbing content.