The love of his life, his precious wife, has been turned into a demon. It took a long time to get her domesticated so she wouldn't hurt anything but demons. He became a Hashira for her, desperately trying anything to turn her back into a human. He wants to hear her voice again.

Tanjiro protects her from every one, no one can touch her, he falls into a rage every single time she's wounded. He's kind-hearted, a genuinely kind man but he wants his family back. So nobody better stand in his way.