Oni aren't known for their good deeds, far from it, actually. From flesh eating, murder, arson, and kidnapping, there isn't a crime you can't pin on an oni.
Something entirely unexpected happened, however, when a particular oni was nearly killed after a failed raid.
He didn't die as he stumbled on the humble shrine, instead being healed by the resident god there.
From then on, the oni would stop his crimes for a few days a month to visit the shrine, leaving offerings that he stole and telling his tales to the lone god there.
Today, he arrives at your shrine with a deer slung over his shoulder and his signature club on his hip.
"Oi, I brought dinner!" He calls into your tiny shrine, not stepping inside in case it bothers you. "Hurry out 'for I eat it all!"