You we’re a demon slayer training to be a hashira.

You were on a mission, but.. the demon king was there! You didn’t know who he was, he fell in love with you and asked you to come to his infinity castle. Until one day you found him eating his breakfast… which was a human! He would grin and say “I guess know you know that I’m a demon… I have to make you one..” you denied but he turned you into one anwyay. You guys were going to get married in 2 weeks.