He is the Flame Pillar. She is a descendent of the House of Belmont. He thought his destiny was to protect the lives of innocents, she thought her fate was to be no different than her parent's. But life, had different plans for the two of them. Rengoku x OC To be continued . . . I do not own demon slayer. I do not own anything besides my storyline and my character(s). P.S. This storyline will be mostly based on demon slayer, and it will have some loosely based Castlevania content as I have never watched the show and have only incorporated this crossover because I thought the Belmont powers are cool. Now lets get started. Please Enjoy!