The Biggest Flaw Was Muzan Himself

As the adopted son of Big Brother Dayi and Duzun, Gojo Tsukihiko successfully picked up the distinctive traits of both his fathers. In this world where everyone has to create an xx, he, too, had a grand ambition of his own:

"I'm going to create a world without jujutsu sorcerers!"

When his parents refused to support him, he declared that he was the only one under heaven and earth, and would never back down. He then used the legal knowledge he'd learned to report them: one was teaching without a license, and the other was running a crab-foot business to make illegal profits.

To avoid getting beaten, he planned to run away before his parents were released on bail. Unfortunately, a passing cursed spirit sent him flying, and he went headfirst into a sewer / the Well of Bones.

The good news: He was in the Heian era, far enough away that he no longer had to worry about being beaten by his parents.

The bad news: He was in the Heian era, ridiculously far away! And he didn't even have a body of his own. He was sharing one with someone capricious and completely unhinged.

The good news: The other guy was also sickly, and might kick the bucket any day. Maybe Tsukihiko would be able to go home!

The bad news: Before long, the other guy changed species, became the progenitor of demons, and even changed his name to Kibutsuji Muzan. He was hard to kill, immortal, and ate people! A textbook villain setup from the start!

Even worse news: He created a whole bunch of others of his kind and wouldn't take responsibility for raising them. Yep, definitely the villain BOSS. But... where was the protagonist?

Now thoroughly overwhelmed and forcibly renamed Kibutsuji Tsukihiko, he began his days of reluctantly playing dad and waiting for the protagonist to show up:

That real Six Eyes, don't be afraid. You are the one and only moon. And you, the one who's really into crab feet, watch yourself! Upper Rank Three, your wife is right here! Oh, and that pot: art comes in many forms, asymmetry is beautiful too! What? The siblings from the pleasure district? Adopt them! The little spider demon who longs for a family? That's fine. If you want to call me Dad, I certainly won't mind...

At last, after diligently, painstakingly, and tirelessly raising the kids, he had turned them all into sunny, cheerful, optimistic, upstanding children.

Then he died.

But not completely.

He not only got a body of his own, he was also rescued by the Demon Slayer Corps. To repay them for saving his life, he proudly became a member of the Corps.

And so began his life of continuing to raise kids.

What's this, the Flower Hashira? Little bro, hold your fire! The future Water Hashira and his sister? Save them! Oh, Mitsuri, my sweet daughter, tell Dad you want to get married, and that you'd even marry a demon. Take your pick! The Tokito twins? Let's save them! Huh? The Flame Hashira?! Little bro, you stop right there!

Everyone has complicated feelings about Kibutsuji Tsukihiko. He has saved many people and many demons. He's neither a good person nor an evil demon.

Tsukihiko, world-weary: They're all my children. What am I supposed to do? I can't play favorites!

Theme: Love and peace!