After Marrying the Sun-Breather, I Was Forced to Go Straight

[Content warning!!! This story's pairing is Kokujiro Yoriichi x Kibutsuji Muzan. Muzan is female for almost the entire story. He only returns to his original body for a very short time in the middle, and there will be a pregnancy and childbirth plotline. The story has now become a multiverse story, yay! If you can't accept this, please leave. This is a Yoriichi x Muzan pairing, so if you can't get into them, this will hit you like a bolt from the blue.] During the Sengoku period, Kibutsuji Muzan finally found the Blue Spider Lily he had searched for for so many years. He would have to spend decades as a fragile human with rare blood, losing all his memories in the process. Only after the medicine had fully taken effect could he absorb it completely and become immune to sunlight. Muzan would do anything to survive. So, using the Blood Demon Art of a subordinate who could see the future, he found the strongest human about to be born. The best way to secure himself a powerful protector was, of course, to become his wife! Then he died on the night the strongest fighter in the world went out to find a midwife. Kibutsuji Muzan, who failed to absorb the medicine, regained his memories, and wasted more than a decade for nothing: … It's all Yoriichi Tsugikuni's fault!!! * Years after his wife and child were killed by a demon and he joined the Demon Slayer Corps, Yoriichi Tsugikuni finally discovered that his deceased wife had been the Demon King. He faced the Demon King, who had returned to his original body years ago, had never dissolved the stillborn fetus, and seemed to have settled down in recent years. After seeing him, the Demon King glared at him, eyes red with anger. Yoriichi Tsugikuni: … There's still hope, probably. Theme: Guiding a person burdened with grave sins onto the right path