Both of them are breathless, it means they can't use any breaths like demon slayers and pillars can do. Yumi and Senjuro are breathless and that's their destiny. They promised to help each others back.But what if Senjuro suddenly changed, that he suddenly become a demon slayer and can use breaths anymore. His attitude also changed and it feels like he is in darkness. Can Yumi saved Senjuro without breaths?

This started as a small idea. Just a bit of a "what if..." but since I love Kimetsu no Yaiba too much, it spiralled out of control and well... I have a lot planned, but I'll take it one at a time. So! This is a Reader x Rengoku au story. Of course, there's scenes with other characters and a whole plot I kinda have planned out but Rengoku is a bab so I'll try to focus mostly on him. The au affects him too so- Ahem! Anyways, it'll start a bit slow and I don't have a set update schedule so I hope you'll bear with me. Hope you enjoy the story! Disclaimer! Kimetsu no Yaiba and all it's characters belongs to Gotouge Koyoharu, the only thing I own is this plot and the Breath of Sparks. Warnings/Triggers : MANGA SPOILERS, violence, blood, death, language(mostly cuz Sanemi), angst, dismembered demon parts(?), idek what to put in this, crippling diabetes (I hope), and Rengoku's overwhelming fabulousness.

My name is Y/n L/n. I'm a demon, true, but I'm different from other demons in this world. Anyhow, I started working for this demon hunter which is a stupid idea. And I began to fall for him. (Dante X Reader, along with a slight Black Butler crossover you'll find out about when you read) [Everything goes to their respective owners, I only own any OC's and any pictures I specify]