A surprisingly good series that doesn’t overly resemble anything else (that I’ve seen/read, apart from its use of common genre tropes like gamified dungeons), Seija Musou remains consistent through its first seven volumes. Character interactions are entertaining, there’s no weird fanservice, and the world-building is solid.
Only real issues would be the introduction of a ‘slaves want to stay slaves’ trope (which fortunately, eventually, gets resolved) and the protagonist’s oddly strenuous objections to revealing himself as a reincarnation in a world where reincarnations aren’t exactly rare.
The eighth novel is a bit of a different story though. That’s where the forward momentum kind of dies out and event developments start to take on a sort of episodic and random/arbitrary feel. A feeling which persists through the ninth and tenth novels as well. I wouldn’t go so far as to say this segment of the series is bad, but it’s definitely disappointing and doesn’t engender much hope for a proper conclusion.