You need more than just turbo yeast to make a barrel of ale in 8 minutes. That being said, what's "elf mead"? It's pretty strange he unlocked such a thing, instead of simply "mead".
I'd have preferred if this remained monogamous with Sylphy. I'm not terribly upset or surprised it didn't because this is fantasy manga. The dude still wearing the slave collar bothers me more, honestly, even if I only notice it occasionally. One thing I really don't want to see is Kouseku purchasing slaves. I'd say that's unlikely, considering the setting and circumstances, but he's still, on paper, a slave himself, so it's definitely not impossible.