The way to him

What if tanjiro had two dads and one was also unknowingly and accidentally Muzan, and he was born half demon half human. So when nezuko went down to town because Tanjiros mother decided he needed a break; she comes home to her mother and younger siblings dead and tanjiro no where to be seen. The next thing she knew she was getting trained by a retired hashira. She promised she would find out what happened to her brother no matter what it took.

While nezuko was doing her own thing Tanjiro could be spotted with his "father" Muzan, his demonic side growing bit by bit everyday. Yet being Tanjiro he keep ahold of his humanity as much as he could. Only enough to not crave humans. Muzan would never let Tanjiro leave his sight. If he did we was kept by an uppermoon, not for very long though.

What Muzan doesn't know before leaving him with uppermoons is that it'll give Tanjiro an advantage.

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This story will end up having inotan and Kananezu as the main ships so if you don't like one of those or don't want to read a book with them in it please don't start this one!! :)