"Kono Subarashii Sekai ni Shukufuku wo!" (bless this wonderful world!) volume 16 by Akatsuki Natsume. Our party of have split two ways, but both teams ended up advancing toward the demon lord's castle. We are entering the final stage with this volume.
Recall the objective from volume 1 was to defeat the demon lord so that Aqua can return to her original post, but the party mostly had not been intentionally working towards this goal. This changed at the end of volume 15 where Aqua ran off to take on this task on her own (enthusiastically at first but reluctantly in the end). Kazuma followed suit in this volume (reluctantly at first but enthusiastically in the end). In the process, we learn that Aqua's open secret about being a goddess was fairly well known, Kazuma has one special intrinsic that turned out to be as useful as his luck, and that both Kazuma and Aqua would perform quite well on separate parties but it would be boring for everyone involved.
Regarding Kazuma's extra intrinsic -- Kazuma had a level reset event in volume 15, and in theory it should have been the end of all adventures and start of retirement from then on. But such relaxing life wouldn't be fitting for this novel series, and our hero has discovered a way to level up and earn skill points fast. It's like the "exploit the game" themes common in Sword Art Online, but here in Konosuba they are more transparent about straight up cheating the system. The end result is an exciting dungeon run done with the classic Konosuba humor, and an absolute highlight for this volume.
The end is near and all the important characters are gathered at the demon lord's castle. Not sure how many more volumes there will be, hopefully it will be a silly ending ahead.
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Next (2019-12-25): "Dengeki Bunko no Hirugohan!!" by Eranto