Onryoki is a giant red demon born from the amassment of vengeful spirits. Half its face is a burning flame of anger, while the other half is warped by rancor. Countless spirits give it an eerie appearance, and horrendous voices emit from its body. In phase one you want to bait him into attacking and then hit him. If he swings his chains around, dodge backward and then charge in and hit him. This phase is simply rinse and repeat. In phase two or when you fight him on the sub mission, his attacks become more erratic. You want to bait him doing an attack that lands him motionless for a second or two where you can get in a few hits. Just keep dodging until he does one of these attacks and then hit him a few times and repeat. .

As found on Youtube