Japanese Demon Folklore

My tatoo artist told me a story about a japanese demon that carried the heads of those he killed on a rope like an old samurai. He met buddha and after became a gaurd to a gate to buddhist heaven an collected the heads of evil men and demons while he helped gaurd this gate. I cant remember his name, does anyone know the name of this demon? Or the where I can find this story?

Well, old samurai were not supposed to do something as disgraceful as to carry the heads of those he killed on a rope, and Buddha is supposed to be from India, but the first thing that came to my mind reading your post, as a Japanese resident, was Nio-sama. But I'm not sure if they ever collected heads.
https://en.wikipedia.org/wiki/Nio