I’m looking for a comic, possibly manwha, that is completed, has a mix of flat coloring and black and white and whose story is about some sort of demon lord that fell in love with a human and is now waiting for her reincarnation. He cosplays as a student and lives atop a school with his female underling.

Spoilers below

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Over the course of the story it is slowly revealed that his underling is secretly working to trigger him into changing into his demon form and end the world/humanity. In the end she succeeds at first, he changes into a giant demon bear form, but I think she sacrifices herself to calm him again.

That is all I remember. My search wasn’t successful, so I wanted to ask if any of you recognize my ramblings.