You can melt him pretty quick with Pest Threads. Try to hit his head in the 2nd phase. Blue Dancer Charm + no armor helps because Pest Threads only does physical damage. Seppuku your health down to proc the Red-feathered branch sword talisman.
Setup:
No armor
Pest Threads
Blue Dancer Charm
Flock's Canvas Talisman
Faithful's Canvas Talisman
Red-Feathered Branch sword (seppuku health down very low)
Faith-Knot Crystal Tear
Winged Crystal Tear (I found out later this does not help with the Blue Dancer Charm. Use something else like one of the stamina or FP related Tears)
