Raid - Gorikimaru | Fate Grand Order Wiki

Boss Statistics

Active Buff		Increases resistance to Buster cards by 50%
Skills		Reduces all enemies' critical attack damage by 20% for 3 turns
NP Effect		Deals around 6000-6500 damage (3BP) to all opponents and inflicts a 1000 damage burn for 5 turns

Kiyohime Statistics
	HP	20,000 - 600,000
	LVL	23 - 75
	Class	Berserker
	Skills	Has access to all three of her skills
	NP	Transforming, Flame-Emitting Meditation: High AoE damage + Stun chance

Battle 1/2	22,500 Vile Oni	15,000 Lesser Oni	22,500 Vile Oni
Fatal Battle 2/2	6,000,000 Gorikimaru		600,000 Kiyohime

Do not forget: Exploit wave 1 to generate as much NP gauge as possible.
Wave 1 contains two Vile Onis, who can put out a fair amount of damage if left alone. Consider using a (small) defensive cooldown during turn 1.
Kiyohime, despite being a Berserker, doesn’t actually hit for much harder than Gorikimaru.
Kiyohime is very squishy and will fall very quickly if focused or hit by a Golden Sumo infused AoE NP. It should be relatively easy to kill her before she can NP, if not in one turn.
Gorikimaru’s buster defense buff is more a detriment to Berserkers than it is to Assassins.
Yet, his critical damage down skill will hamper any critical-focused strategies. Spamming Assassin NPs is ideal.
Gorikimaru’s NP is much more lethal than it appears. The burn damage is substantial and may even grind down your Assassins in time.
As a Rider Gorikimaru is also more prone to dealing critical hits.
Despite facing a Rider opponent, bringing caster supports is still viable, if a bit more prone to receiving lethal critical hits.
Gorikimaru is generally considered the most troublesome Oni due to his Buster Protection. Eating plenty of beans of various kinds will help the clear speed immensely. The QP from trading them in might not be worth the hassle of each raid taking longer.

Try to field set-ups with two Servants that provide offensive buffs for one main DPS with Golden Sumo equipped.
But don’t leave the main DPS entirely undefended, especially if the DPS is a Berserker.
Ideally, a set-up would be Main DPS / Support / Offensive Hybrid or Main DPS / Support / Support.
Field additional Supports or Hybrids in the backline as generally the Main DPS will not fall first.
A team-wide cleanse, or using the Rain of Isis from the Atlas Academy Uniform can be very useful in removing the burn effect. However, reducing cooldowns for Assassin Servants isn’t as powerful.
The Chaldea Combat Uniform remains a safe option as well.