While I can understand why Seirei Gensouki would want to draw out – and thereby end the season with – rescuing Celia from her twit of an almost-husband, I'm not sure that the emphasis was quite in the right place with this. By all measures, the penultimate episode of the show should be fraught with tension, especially since Rio's first real ally is about to be forced into marriage with his first true nemesis.
Of course, this could simply be a case of chickens coming home to roost – because the series flew through the source material so callously, none of the characters are quite developed enough to make this the episode they deserve. Although Rio spent a lot of time with Celia in the first part of the series, their relationship didn't get much beyond superficial, although in its defense, it feels more solid than most of the other Rio/girl relationships that followed. Likewise, Charles was never given the chance to have a whole lot of motive beyond that he really enjoys having power over others and abusing that if given half a chance. While that isn't a terrible characterization for someone we're clearly supposed to hate, it also doesn't do the plot any favors right now – especially since we don't get the idea that Celia's father has as much power as his title would suggest. Why does Charles want to marry Celia so badly then? Does he just not have a loli character in his collection of wives?
I do kind of wish that we'd known that polygamy was practiced in Beltram before now, because that could certainly have given us some insight into Charles and the political implications of his marriage to Celia. As it stands, the reveal of his many other wives simply feels like a cheap way to show that Celia's life is likely to be unpleasant not just because of her husband; wife number one doesn't seem like she's thrilled to get a seventh lady in the household and is clearly planning to take that out on Celia. It's also very obvious that Celia has zero interest in actually marrying Charles; she's only doing it because she seems to feel that she has no choice. Again, knowing more about the political situation would have really helped here – we know that one family has fled, but how has that impacted the remaining nobles? What has it done to the royal family's hold on power, and are they nothing more than figureheads at this point? That certainly seems to be the implication, and that marriage to Celia is another way for Charles and his family and followers to further cement their hold on the kingdom. Celia is looking an awful lot like a trophy and a means to an end; that Charles seems to be attracted to her may just be icing on the cake.
Because we have so little information, that detracts from Rio and Celia's reunion, mostly in that her actions don't make a ton of sense. She had the perfect opportunity to just run when Rio showed up in her room – he's clearly powerful (or at least more powerful than when she saw him last) and he wants to help. My best guess is that Celia is afraid of what the consequences will be for her father if she lets Rio take her away, but confirmation would really have been helpful here. She's not acting in her own best interests and while I applaud Rio not trying to override her wishes, the whole thing just feels a nit nonsensical and underwhelming. That's a shame, because it really feels like there's a lot of meat to this bit of plot, but like Celia at dinner, we're just looking at it without partaking.
Since the storyline is being drawn out to the final episode, there is a chance for things to end with a return to the promise that opened the season. Seirei Gensouki still has potential to pull from if it will just rely a little more on its story and less on the boilerplate isekai tropes that it seems to think are its chief attraction.