I was having a hard time but finally cleared it... 

The thing is, vernal jade is way better for kezhou than sacred favour. However, my vernal jade was 40 lvl, so I used sacred favour until my vernal jade was 80 lvl. Why, you ask... because I don't like doing termination and mediation over and over again. I can bear defence, but not them. And that's the reason most of my weapons are between 60-70lvl

I have only tried 3 melee weapons for him: momiji itteki(s5), vernal jade(s0) and sacred favour(s1). The best one among them is vernal jade. I think there isn't a big difference between momiji itteki and sacred favour. But sacred favour is slightly better. Another good thing is vernal jade recently added to the shop, so smelting it is easier.

I'll continue trying out different weapons for kezhou...

Also, I got this polearm weapon skin about 2 months ago, and it surprisingly matches kezhou perfectly. So I use the skin on vernal jade! ☺️