The conclusion to Nidome no Yuusha wa Fukushuu no Michi o Warai Ayumu starts out immediately from where the previous novel left off, proceeds to waste a bunch of time on detailing the vampire’s history, and then ends in a remarkably aggravating manner.
The harem of yandere ending the way it did was I suppose one of the better results you could expect from such a thing, but the final revenge scenario is just pure brute force. It lacks any of the inventiveness the earlier ones had. The elf never being mentioned again is also an issue (would’ve rather had some backstory on him instead of the vampire) and it’s annoying that we never get any focus on the last couple of hero party members. A near total disappointment in the end.
I ended up reading the fifth Saikyou Onmyouji no Isekai Tenseiki novel, days before its official release date, due to a publisher error that replaced the contents of the the fifth Otome Game no Heroine de Saikyou Survival novel with this instead. While I don’t recall much of the series from the Anime adaptation, jumping in here turned out decent enough since it begins with a fresh start of sorts for the protagonists. That said, most of it is pretty generic with only the interactions with the demons sparking any interest.