Mikio - Sumo Oni Hunter

Not a bad idea, however tattoos are typically associated with the Yakooza in Japanese culture.
So, with that in mind I would suggest one of three things:
1. Lose the tattoos entirely and replace them with even more pronounced scars (taking note of the typical claws and mouths noted in your typical Oni for reference).

or, if you really want to keep the tattoos

2. Replace each of the frivolous designs for guardian spirits (so I believe the tiger would be able to stay, but things like the ocean wave and the woman would need to be replaced).
3. Keep him as is, but have his backstory include something like he devours the oni afterward in some design to try and incorporate their power into himself, and is otherwise a pretty immoral figure but he hunts evil monsters to prove who the 'ultimate monster' is so he's tolerated by general human society. Maybe he even sponsors himself in sumo tournaments with rare horns, bones, or other monster derived objects and/or medicine as part of the tournament prize.