At this point is a blackmail still possible? The picture was taken like few months ago, would it still count?
MC coming up with the challenge at this point kinda fucked up, no way he wins and that gonna be another pointless loss. This girl need to learn some respect for him, maybe the editor helped her by giving her a chance to draw but if that was all he did its kinda stupid she behaves like that.
I would like some separation arc(i think it might happen at some point, its kinda needed for the girl development) so the girl can realize how much she relies on his help and how much their "challenges" improved her mangas.