Either the artist wasn't trying to conceal it at all, or they greatly overestimated how much the silhouette actually accomplished. Rather than guesses, we know exactly who were supposed to suspect. Making it quite that apparent while trying to obscure it at all kind of makes me suspicious that it wasn't just that dillweed in on the action though? Basically everyone in the class hated the MC anyway, because they're childish twits about someone the idolize being friendly to someone else.