A late review, but I don't have much to say.
I'm glad to finally see more from Yihwa/Ehwa after she's spent so many chapters doing very little. Yes, she got her time in the limelight against Cassano along with Wangnan, but that didn't last long. It seems hopeless for Prince, Miseng, and Akraptor, but she might actually get her own fight scene soon.
For the matter where is Cassano? I don't think he's really done anything since boarding the Hell Train, and he's supposed to be the entire reason the heroes came there in the first place. I really dislike the Jedi robes Hoaquin's team are all wearing, they make it a pain to differentiate each team member. I'm not even sure how many people are on his team at this point; it seems like there's a lot of characters on that side that sort of disappeared between arcs. What ever happened to Michael, Apple, and Traveller? I think the Traveller might still be with them, but he's wearing that robe so I can't tell. Overall, there's too many characters on either side for me to keep track of, and so many of them I don't care about.
A prime example are the two travelling with Ehwa, Bero Bero and Pompidou (had to look up their names). They've been recurring background characters for awhile, just doing their own thing until they got mixed into the fray and suddenly started receiving focus. While I don't mind that happening in and of itself, with SIU it happens much to often - almost always to the detriment of existing characters. In the next arc, if they don't disappear altogether, the same thing will probably happen to them. I just wish the series would stick with the characters it already has and develop them instead of overhauling the supporting cast every arc.
Maybe if they'd stuck with the characters that passed 2f at the end of Season 1, even the background ones, and developed them over time instead of constantly changing up the cast, I would care a lot more about what is going on in this arc. Team Tangsooyook from the start of Season 2 seemed like they were heading in this direction, but even they have been shafted by the constant influx of new characters many of whom are much stronger (and thus more important) than them.
*Sigh* I still fondly remember the time when Akraptor and Horyang went toe to toe with Viole in a Mêlée à Trois back at the start of the season, but now Horyang is unconscious in a hospital some 8 floors below where the cast is now while Akraptor is stuck in a cage.