By request: the Sequel, Sunlight From The Ashes, is now up if you would like to read it. :)

Thank you for your support.

Also, posting the full summary here because ffnet doesn't ever give enough room or formatting:

Sunlight From The Ashes (AKA The Return of the Sun Smile)

It took Kamado Tanjiro a dozen loops to realize that saving his family meant becoming a demon.

It took him half-a dozen more loops to gain control of those demonic instincts.

It took him dozens and dozens of loops to FINALLY find the solution that keeps his family alive and allows him to live as a human and become a demon slayer again.

...Or does it? Because Demon powers tend to be unique and have chaotic side effects that Muzan can't predict.