Warning! Massive spoilers ahead for Black Clover!
There had never been any doubt originally that Black Clover was about the friendly rivalry between Asta and Yuno as they strove to become the next Wizard King, that is, until the introduction of the devil Liebe. Now it's clear that Black Clover is actually about him.
Part of what initially caused so many fans to flock to Black Clover involved the well-executed retelling of a compelling trope in manga. A powerless boy desires to become something that is wholly contingent on him possessing powers but ends up following his dream regardless via an unprecedented method that highlights his own specialties because only he can attain it. For Asta, it was when a five-leaf grimoire possessing anti-magic chose him, bestowing upon the magicless boy a power that enables him to eliminate all spells—almost like magic itself. But where did this anti-magic come from? As revealed in chapter 268, it came from Liebe, proving that Asta is actually part of Liebe's story.
Asta is essentially the human version of Liebe. They were both born powerless and mocked by their betters perpetually. Like Asta, Liebe's weakness ended up defining him for the better, since his magicless state allowed him to enter the human realm and meet Lucita, a woman he later comes to cherish and connects him with her currently unborn child Asta. When a powerful devil later attacks the two, Lucita seals Liebe inside a grimoire to protect him until he became strong. Inside, Liebe's hatred for his own kind festered to such an extent that it eventually manifested into what is now known as anti-magic.
Black Clover presents this incredible story only to the reader during a time when Asta and Liebe are struggling to perfect the so-called devil union, a fusion of sorts that will allow Asta to wield the full extent of Liebe's powers and unlock his complete devil form. As of now, Asta's only motivation for going into battle (where he's now fighting against The King of Devils Lucifero) is to save the captains Yami Sukehiro and William Vangeance who a trio of Spade kingdom subjects known as the Dark Triad captured to basically open the gates to hell and, of course, to stop these gates from opening. But Liebe's motivations are much more involved and deeply intertwined with his own history. That's because this battle is a continuation of Liebe's broader story. To Liebe, devils are the equivalent to Asta's muddled relationship with nobles and royalty. If this were truly Asta's story, then they would be fighting the people who looked down on him in the Clover Kingdom. But that's not the case. They're fighting against the devils who mocked Liebe as a child, separated him from the one living soul who cared for him, and caused him to create the powers that both drive the entire story and are the key to defeating the devils.
More importantly, stronger connection to them than Asta ever will. So long as Liebe stays in Black Clover, he will forever be the true protagonist.
