[Snake]

I believe Sayakensa should have a penalty attributed to Light Resistance instead of VIT.

Maybe a debuff that whenever you damage someone with your Katana, it reduces your Light Resistance by 5%, up to a maximum of LV5, but anyone you attack and damage with your Katana receives a debuff to their Dark Resistance by 10% per LV.

It's hard to decide if it should be a big number, since 100% Darkness Resistance is possible, but that might help. Still believe if you proc 'Resist!' on Darkness, it shouldn't lower your momentum.