(Disclaimer: I guess my favorite character is technically a spoiler so beware)
Demon Lord had no right to be so enjoyable. Every sign pointed to it being absolutely awful in every way. It was the perfect storm of awfulness that has plagued seasonal anime for the last five or so years since Sword Art Online popularized the isekai genre, but here we are, How Not to Summon a Demon Lord being actually pretty fun. Not great or even pretty good, but a lot of fun. Fun isn't something we think about much when we're scoring shows and putting them on our "completed" lists, but for some reason, Demon Lord makes me remember how fun watching anime can and should be. A lot of you may be thinking that I'm making a mountain out of a molehill, but I can't find any other way to describe Demon Lord's charm.
Aesthetically, Demon Lord doesn't do much to stand out from its fellow isekai shows, using the same bright color scheme to emphasize how it takes place in a game world, uses fairly generic fantasy creatures, etc. There's really not much to be blown away by visually in Demon Lord, which I can't imagine being a big draw for most people anyway. I mean, it's yet another isekai power-fantasy, how unique can it be visually? Something impressive is how Demon Lord somehow manages to make impressively skimpy female outfits following it up with an even skimpier outfit the next episode like they're having a competition with themselves. Not a complaint, just an observation from an interested viewer.
Sound design is a little more impressive. There were moments that I was simply pulled into because of how solid the soundtrack was. The theme song that they use to introduce the paladin character, Saddler, was especially epic in my opinion. However, I wasn't really impressed with either the opening or the ending, though they were both fairly mediocre. The magic sound design was also pretty good, but I don't know if I can really call anything too bad after watching Fate/Apocrypha.
Favorite Character: Krebskulm
That's kind of a good segway into talking about the characters, which play a huge role in making Demon Lord so enjoyable. Individually, they really aren't very unique, but together they have such good chemistry that you have to smile every time they interact, especially the main trio. In fact, Diablo, the main character, is the reason to give Demon Lord a shot. He starts as just another shut-in (where have I seen this story before?) before getting transported into the game that he is an apparent master of. Seeing how socially inept he is on the inside, only able to pull off an arrogant and cocky attitude is a lot of fun. It blows up in his face a lot, putting him in awkward situations, primarily with women, creatures with which he is very uncomfortable.
Demon Lord is just a blast. Obviously, if you want to watch a serious story unfold, Demon Lord probably isn't for you, despite the story being pretty good actually. There's really not a lot more to touch on, obviously it's kind of risque, which doesn't bother me at all, but some are really turned off by ecchi, which I understand. If you're someone in the latter group, you're definitely not going to like Demon Lord, since some scenes can be borderline hentai, so there's that. However, if you just want to watch a fun show, not a lot of depth or complexities, then Demon Lord may just be perfect for such an occasion.