The Cost of Pride~ Kokushibo x F! Reader (Completed)

Warning: There will be spoilers from the Kimetsu no Yaiba manga! You have been warned. Almost 400 years ago, a man who was once known as Michikatsu Tsugikuni had grown up with a young demon slayer that he had grown feelings for. Despite his jealously for his younger twin brother, he did everything he could to impress...