Oh look, yet ANOTHER "an MMO turns real and the protagonist is trapped in his avatar" anime. That's really the flavor of the month in Japan right now, I guess.
This one has a slightly interesting twist, though. In Sword Art Online, or Konosuba, or In Another World With My Smartphone, or Log Horizon, etc, the main character is (to varying degrees) what one might call a "hero." Not quite so, here.
The main character here is the guild master of a defunct top tier guild whose other players have all moved on. After 12 years, the game "Yggdrasil" is finally shutting down, and Momonga sits alone at the round table in his guild hall, reminiscing with bittersweet fondness about the accomplishments of his guild that are about to fade away forever. He's stayed in the game alone for a long time, unable to bear the thought of his and his friends' accomplishments fading away or falling into disrepair. So he has kept a solitary vigil, maintaining the guild hall and its NPCs, until the very end.
The appointed hour of the game shutdown arrives.
But Momonga is still here. He tries contacting a GM to see if the shutdown has been rescheduled, only to find that the message fails, and he can't contact any other players anymore, either. In fact, his UI is missing, and he now notices that the NPCs are actually moving their mouths when they talk, and he can smell and touch them. Checking the environs outside his guild hall, the landscape is completely different. He, the guild hall, and all its attendant NPCs and treasures have been transported to a new world. One he can't leave - and he's not sure he would really even want to anyway.
Here's the twist. Momonga is a greater lich. The guild was a PK guild, the guild hall is "The Great Tomb of Nazarik," an immense labyrinthine extradimensional mausoleum, and his now-living and intelligent vassal former-NPCs are all vampires, demons, and monsters that worship him as a living god. Momonga renames himself after his guild, Ainz Ooal Gown (seriously, yes), disguises himself, and heads out to perform great deeds in its name, so that any other Yggdrasil players that hear about it will recognize the name and, hopefully, come running. Momonga, or rather, Lord Ainz Ooal Gown hopes in particular to be reunited with his old guildmates. And, while he's at it, maybe he'll just go ahead and take over the world, since as far as he can tell, the most powerful beings on the planet aren't even half as powerful as he is.
It's got some teeth to it. I have to admit it caught and kept my interest right off the bat.
But, naturally, I have some gripes. And they're not trivial gripes.
First and foremost, this show is WAY up its own ass. Everything is SUPER SRS BZNS, in a crapsack world setting. And it's not afraid to spend an entire episode on needless and meaningless waving of arms (and flapping of gums) that serves no purpose other than to say "Check out how cool this shit is, aren't you impressed?"
Second of all, like IAWWMSmartphone, the main character is pretty much nigh invulnerable. Unlike Smartphone, however, Overlord tries to put on a paper-thin pretense that he might not be, even though he always is. And it spends too much time on it. There are other interesting things going on in the periphery that deserve more screentime than Lord Ainz butchering yet another trashmob.
Third of all, there are pacing issues. Too much time is spent on tedious things (especially the things involved with gripes 1 and 2), and not enough time on exploring the interesting parts. The last 3 episodes of the season were particularly egregious in this regard, stretching out a battle in a manner the like of which I haven't seen since Dragonball Z 20 years ago, with no real reason to do so. I don't know why these writers think shouting attacks and real-time mockups of MMO-battle dynamics are still interesting. There was more interesting plot development during the ending credits of episode 13 than there was in the actual episodes 11, 12, OR 13. It started to feel like a story being told by a 4 year old - you know, the kind that goes on forever because the kid keeps getting bogged down in details that don't matter. Which is really a shame, because the first 10 episodes were pretty engaging and didn't have this problem quite as acutely.
My final gripe is that the show can't seem to decide whether Ainz is a villain or an antihero. It toys with the idea of him redeeming himself and becoming a hero, inspired by the example set by one of his guild mates, but the next moment he'll be callously disregarding human death and acting as a true lich would - cold, calculating, uncaring. He'll save a village one day, the next day he'll be completely unmoved by the slaughter of the group of adventurers that he was, for all appearances, becoming friends and close compatriots with over the course of several days - and despite it being in his power to resurrect the dead (and not just reanimate them a la necromancy), he never even considers using it even in the face of truly poignant death of characters whose backstories were just beginning to be explored in such a way that the audience was clearly meant to believe they'd be recurring.
Despite all that, I think I'll be watching season 2, as soon as it is dubbed into english. This series is way too dialog heavy for me to bother with subs.