I think Enzo needs to decide. Well, he needs many things, including becoming a real human being, haha, anyway... in the analogy the mad Geppetto gave Pinocchio (read grandpa and Enzo), there were two different sets. One was the "valuable things that try to break free", while the other was, "if you want a caged bird, you'll be...", ah, ok, what he said.
And it seems that at this point, Enzo's not sure how he wants Rian: a caged bird, or his ultimate gem. That's why he keeps treating him like he wants to impose full control over him and then gives him vast openings. Enzo's acting so confusing because he is a very confused character. So eventually, he needs to decide. Well, he might need an external element to reach that decision, but since it's romance and not horror, I'd say he's gonna make the right decision in the end.

We all know Enzo is smart n all but letting go of Shadow wasn't a good move from his side unless he has other means to keep Uno in check but it would be fun if he let go of Shadow cuz he was arrogant enough to make mistakes but then again it could be cuz he likes "valuable things that try to break free" and purposely let things lose so he can play the tag game, the way all of them can be fun if executed properly (≧▽≦)/