@faiheartles
I'm pretty sure he can't eat them both because he and Kliera made a formal contract (on her blood and all) that he will eat only her. He may honour it but Luslia sure as hell ain't having it, as we saw her throwing a tantrum in this chapter
Not to mention he still thinks Kliera's "Cleaning" is the supreme magic so wouldn't adding Luslia's magic onto that be kinda superfluous?
And it's not like he can tell Luslia he'll eat her after Kliera. The whole point of this chapter was her pressuring him into eating her and only her. You don't tell a woman with crazy heart-shaped pupils you'll choose her after someone else.