Damn, making me feel small. I spent hours on that, we'll a good chunk of it being passive attempts but still, many deaths. Many tries.
Well that puts me at ease on how hard the Owl must be. You kept saying the Owl, and Demon of Hatred were utter BS. But I had Genchuro figured out after about ten or so fights. He always counters after your second attack or not at all. His last swipe on his big combo can always be dodged, and then countered for free damage. When you heal he shoots his bow at you, but you can dodge that and counter for free damage too. Keep slashing and keep him in a corner so he tries to use his bow and gets hit. Catch his thrust attack after he slams down, before the first deathblow. After first deathblow, jump after each slamdown and get ready for a sweep. After that all he really has is his triple shot bow attack, which can be deflected pretty easily.
His storm form is a pushover. Just keep countering the thrust, and get ready to leap at a second's notice to avoid the sweep, or lightning attacks. Storm form keeps trying to use the bow as well, and that's just more free damage.