Responses

I can vouch on the other guy. big eyes and bigger head in anime or in general in terms of drawing usually means they are depicting a child. if I may, I'd compare this to the seven deadly sins, Ban's love interest.
if analyze it enough, even with the huge size difference, it is heavily implied. as I've read the whole story, I only saw his "grown" size once where he looks half decent in one panel, and I believe it was around chapter 7 or 8.
and if that doesn't really convince you since majority already stated their pleas, I guess that's on you now.
People keeps saying the bottom looks like a child....he looks fine, it's the top that's just waaaay too big