Swoosh. Bzzt. Cut.
The red and purple lightning crackled as Eren swung his weapons in the opposite direction from each other. His blades touched Oni King's skin and managed to breach his natural defense layer.
Two distinct cuts were formed on either side of Har Jahar's neck. The blades cut his flesh and penetrated halfway into it from either side.
And yet, Eren couldn't chop off the Monster King's neck. His mana didn't even pose a threat to the monster who was only a step away from becoming a Monster Emperor.
Eren had to struggle to get his weapons out of their stuck places. This whole time, the audience was flabbergasted by what they were seeing and the Oni King maintained a stoic expression on his face.