Board Thread:General Discussion/@comment-24098614-20160522195409/@comment-25942629-20160528135657

Mahiru definitely planned on having Yu become a demon. His personality is perfect before it. Even at the beginning of the series, it was clear that he was one of the worst choices to give a demon to.

Your theory is certainly possible. However, the artist sometimes change the colors like that to make it more beautiful artistically, and it is not something that changes the story. Yu as a demon could certainly betray his comrades at any time, but I am not sure he is intelligent enough to do that. Mahiru was extremely intelligent, even before she became a demon.

We will have to wait and see. Mika and demon!Yu might even give Crowley a run for his money if they are doing what I think they're doing in the next chapter.