Villainess Level 99: I May Be the Hidden Boss but I'm Not the Demon Lord

The Hidden Boss Battles the Demon Lord (1x12)

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At long last, Yumiella and her companions reach the Demon Lord's castle, but his power is so great that she's the only one who stands a chance against him. Then the Demon Lord tells them the true story of his connection to Valschein's royal family.