@Seikirin
This is not chapter 30 in volume order. Here chapter 30 in volume. Look difference. Due to volume 5 does not have bonus chapter "base contain list (index) free sample of vol5", I think this was chapter 34.5 in volume order but I not really sure because I can't read Japanese. Damn magazine order for this manga really fckup.
I like to imagine that, on page 4, all the oni were in different areas of Rimuru's mansion, they ran teleported over when they heard him call "oni", only for them to collapse when he finished his sentence.