In Demon Slayer: I Fear Pain, But I Can't Die

Provisional Blurb

What's it like to transmigrate with an immortality ability you made up yourself?

Ouch!

I was supposed to transmigrate into Bungou Stray Dogs, but ended up in Demon Slayer instead. Well! My situation didn't improve at all. Instead of being mentally and physically exhausting, it became purely life-threatening.

Fortunately, my ability works reliably. It just hurts a little. But I'll get used to it, since I can't die. I also got stuck with an unlucky System. It's not much use, but its main purpose is to provide emotional support.

After wandering for a long time, San Yaozang followed his instincts up a mountain. Before he passed out, Tanjiro's father found him and brought him home. Terrified of the pain that grew worse with every death, he learned Sun Breathing.

And so, San Yaozang spent a warm and happy time with them.

That is, until the story began. Watching Tanjiro walk away, San Yaozang sat by the door with an axe all night. When the demon came, he silently opened the door and led it away from the Kamado family in one breath.

One swing, two swings...

By the time the sky began to brighten, the demon had turned to ash in the sunlight. Just as San Yaozang, covered in blood, was about to collapse, a pair of gentle hands caught him. When he woke, Tanjiro and his younger siblings were hugging him.

And Tomioka Giyu was sitting inside. The first thing he asked was,