Vampire/Genesis (Misunderstanding)

I can't remember when it started, but when he realized it, he was living as a vampire hunter in another world. Due to a curse, there is a wall of separation between his inner emotions and outer demeanor, so without his cheerful personality being known, he is feared by those around him as a madman. This is a story of how such a man—whether blessed or cursed, it's unclear—builds an entire era.