Hmm, problem emerges...Kuro is trying to take control over Azul...Azul is trying to absorb power from all the demons around him. Kuro trying to pull Azul back who is trying to fed off of all demonic power around him...so technically Kuro would be linked to all those Azul is trying to drain at the same time...
This wont end well...especially since Azul is trying to tap into Siera...something bad is going to happen...
That'll be as much to his dismay as hers. Demonic energy might be toxic to her (hence why she got screwed over after TFQ) but that works both ways. Her essence is toxic to demons as well, even if it is mixed with demonic energy.
Done in by the dubious doings of destiny.