I love the art for this arc, not just because it's lovely, but it gives you a sense of scale for just how huge the oni are, their sexual dimorphism, and a bit of variation in their heights and builds. We've seen Ma-Tou (237cm) in relation to the party (1 Crim = 146cm, 1 Hinagiku = 120cm), and seen closeups of the nameless masked male oni before, but that's been about it.
This time around we see that Ma-Tou is fairly tall for a female oni (she's slightly taller and broader than the others in the ladies' hotspring back in chapter 90), and Ra-Sen is both shorter than the swordsmith (~210-ish cm?) and of more slender build. Chief Gi-Teru is just an absolute unit, about a head taller than the other male oni (1.5 Ma-Tou heads, 2 Ra-Sen heads), and is easily more than 250cm tall (horns excluded).
Tsubaki...is just a human-scale girl with oni horns. Both a young oni child and a hypothetical oni with human-style achondroplasia (genetic dwarfism) would have proportionally short-but-chubby limbs; an extremely short oni would still have broader hips and shoulders than Tsubaki or a human.
