Demon Slayer: The Demon King's Sword

Instead of Muzan finding and killing the Kamado's first and turning Nezuko into a demon, what if he found Tanjiro first and turned him into a demon instead? Muzan finds the perfect subject in Tanjiro who has greatest potential in becoming a demon who can conquer the sun. After turning Tanjiro into a demon who awakens, he is ravaged by hunger and Muzan decides that the best course of action is to use Tanjiro to kill the rest of his family to ensure that no other sun breather will arise to challenge him in the future. Tanjiro ultimately kills his family and devours them, but when he comes too he is racked with guilt despite that he has lost all of his human memories. But he didn't kill everyone, because luckily Nezuko and Takeo were away when the carnage started but they had to witness as their beloved older brother killed their mother and the rest of their siblings. Now they are conflicted and they want their revenge, but who do they blame? Do they blame Tanjiro, or the man who turned him into a demon and is manipulating him? Nezuko and Takeo are at a stand still because of their differing opinions but there is one thing that they can agree on. Muzan Kibutsuji must die. And they need to get stronger if they ever dream of accomplishing that. Can Tanjiro be redeemed, or will his newfound loyalty in Muzan destroy what little humanity is left inside of him?