AU. you were nezuko's boyfriend.

nezuko and the others were fighting demons which caused them all to be distracted.

Tanjiro: "these guys are too strong!, he turned and moved to take on some demons while some hashira were fighting uppermoons (in this au there were more than 12 of the 12 kizuki there are 50)

the hashira fought the demons, clearly wanting to defeat them as quickly as possible.

but this led to one thing...

nezuko being left alone..

as 10 demons were about to finish off nezuko and kill her you appeared grabbing the demons fist and blowing away the others which just your arrival.

even though she couldn't speak because of the bamboo muzzle in her mouth, you can tell she was happy to see you, but that didn't last long as she passed out of exhaustion.