Arifureta's recent turn towards irreverence means this reunion actually isn't as bitter or angsty as you might have expected from the initial episodes. The classmates' awkward reactions at Hajime and his gal-pals leisurely strolling into the restaurant they're in is actually one of the better, more low-key examples of when the show makes its humor work. That's coupled with a funny little gag about one classmate not even remembering Hajime's name, though in fairness I don't know that I recall what that guy's name is himself. In general, our lack of context and awareness of who these people are is the biggest issue with what this episode is trying to do. None of these classmates seem to be amongst the few that got developed previously, with hardly any names or even key personality components made clear. They open discussing their own side-plot about some other classmate named Shimizu who's gone missing, and I'm hard-pressed to recall if that's someone I'm supposed to know. I've been hard on the parts in past episodes that tried to focus on the class due to how frivolous they felt, but I can't even say now that they should have spent more time with them to properly set this up for later. It just means when we do drop in on them in a major way like this episode, the show should distinguish them in such a way that we feel like we know who we're apparently going to be spending more time with.
The one exception to that issue is Ai-Chan-Sensei, the adorable tiny teacher of the class who popped up a couple times already in those previous asides. She's the one the story tasks with actually engaging Hajime regarding his sudden reappearance, and they develop a rapport that's just entertaining enough for this episode to not be totally bogged down by it being mostly them sitting around talking about things. Hajime's flippant replies to Sensei asking what happened to him are funny, in-character, and fine for the audience since we already know that story. Conversely, after several spots of her seeming timid and ineffectual, it's nice to see Sensei able to exert some genuine authority, and that contrast lends well to the humor as well. The other characters added into Hajime's group are all interchangeable extras that exist to react to seeing his badass makeover for the first time, but Sensei at least feels like an interesting new addition to the cast that I'll probably enjoy seeing stick around for a while.
Even decently-executed banter can't paper over how much of this episode is spent on sitting around explaining things though. It seems Arifureta just can't find a functional middle-ground, pacing-wise. So much time here is spent on Hajime and his group sitting at a restaurant table, deflecting questions or defending Shea from violently racist Templar Knight (the guy threatens to chop Shea's ears off and Hajime tells her she should just not worry about that, like the people person he is). There's some entertainment value in the aforementioned irreverent humor of the characters' flippant reactions, but it becomes apparent as mere time-wasting until Hajime can break into Sensei's room at night and have a real conversation with her, actually explaining the plot after all this time!
It's been hinted at before, but this is the first time the whole backstory with Liberators who constructed the labyrinths to fight the Gods of this world, who are the real villains, has been detailed so specifically. It works fine as far as JRPG-style plots go and fits with the mechanics of how Hajime's been dungeon-diving and acquiring new abilities so far. But as much as his pointed desire to not save the world after he's gotten all the powers will likely see him railroaded into doing so later anyway, it still perhaps gels too well with the lack of development he has with those nobody classmates so far. He's just a cold jerk to them who, perhaps understandably, doesn't want to deal with their barely-mentioned side-plot. It feels like a bout of forced antagonism, seeing that as he reveals to Sensei, he's aware that there was just one person in the class who tried to kill him. It is probably too early to really judge that element though, as all of them coming with Hajime now surely predicates some level of development between him and his former classmates. We can only hope. Otherwise, this is a transitory episode of Arifureta that exists in service of accomplishing just a couple new plot beats, but wastes too much time in the process.