
I'm not sure if there was intention behind that. I just thought/assumed they looked like that because 1) the female lead was malnourished due to her negligent uncle's family and 2) despite being only 15, the male lead has been participating in battles since he was young so he naturally grew up being big. OR perhaps this juxtaposition of their physical appearances emphasizes the similar power and leadership they have despite their different backgrounds. OR (lol) maybe making the ML look like a "real" 15 year old boy would be even less realistic as he is the master of the castle and is sufficient in battle.
Lol, I don't know the answer and I understand if you feel uncomfortable but... I personally think the jarring appearances of the two leads help in informing us about their personalities and backgrounds!
Bruh when I started reading this I was kinda offed with how childish she looked. There’s only a 3 years age gap between them, yet why did it look like she was 7 and not 12, and him look 20 and not 15????