Playing off these instances as a joke is dangerous as it normalizes sexualizing young characters as well as justifying romantic relationships between children and adults. The author could have easily aged the characters up but chose to spotlight their young ages before sexualizing their relationships. Riko's physical reactions are given top spot.
The camera lovingly frames Ilulu's bouncing breasts while she partakes in childlike behavior. The dragons understand the concept of human ages as they easily adapt the mannerisms closest to their own age, but this doesn't excuse any of the problematic elements. Episode 6 of Miss Kobayashi's Dragon Maid S recently revealed that dragons don't have the same concept of age, which could be the author's attempt to explain away the more problematic relationships.
