Iseleve is simultaneously too short and too long; on one hand it's the typical "season one is actually just the prologue and nothing beyond the rise-to-power arc will happen" scenario, on the other the big USP is that it's both an isekai and irl high school drama crammed into one. Both are actually pretty good and if they were separate shows I definitely would have enjoyed that more than trying to fit 26 episodes of two anime into 13 of one.
Specifically because the last 2-3 episodes are EXTREMELY low quality. I don't know if they ran out of time or ran out of money, but these episodes are very bad, production-wise. Lots of recycled shots, tons of still frames (including an entire minute-long sequence of a plain background with no characters, just VOs), and out of nowhere loads of bad CG. In fact I don't recall any CG prior to these episodes, so either it was done properly or they only implemented it for time/money reasons. It doesn't help that the big fantasy anime trope of a redeemed antagonist along with a new UberMegaUltraMechaDoomLevelSSSSSClass bad guy come up and ruin the fun and free feeling of all episodes prior. The end credit stills on episode 13 are more interesting than the last 2-3 episodes so that says something.
I didn't hate it though. Besides really bad pacing where the irl and fantasy sequences just feel out of order (not narratively, just that the time isn't split evenly in a bad way--difficult to explain but obvious when watching) and naturally the final couple episodes, I have certainly experienced worse in this genre. It's a decent enough show that you won't remember but probably won't regret watching.
