Rising Sun

Otsutsuki Hagoromo can travel through time and space so of course he found his way to the world of Kamado Tanjiro. Tanjiro had survived the final battle with Kibutsuji but with a great sacrifice on his part. Now an immortal demon seeking a successor to the Sun Breathing Style, he met the Sage of Six Path who had foreseen the future of one of his own. A harsh path that he sincerely believed that Tanjiro can help.

Thus Uzumaki Naruto found himself a mentor...