Revival: Onigashima - Return! Kazakoemaru Raid Guide | Fate Grand Order Wiki

Raid Guides

Battle 1/2	20,000 Lesser Oni	20,000 Lesser Oni	20,000 Lesser Oni
Fatal Battle 2/2	6,000,000 Kazakoemaru		600,000 Ushiwakamaru

Active Buff		Increases resistance to Quick cards by 50%
Skills		Decreases debuff resistance of enemy team by 20% for 3 turns
NP Effect		Deals around 6000-6500 damage to all opponents and seals NP for 1 turn

Ushiwakamaru Statistics
	HP	20,000 - 600,000
	LVL	15 - 85
	Class	Berserker
	Skills	Has access to all three of her skills
	NP	Dan-No-Ura Eight-Boat Leap, High ST damage

Do not forget: Exploit wave 1 to generate as much NP gauge as possible.
Sasaki Kojirou has been replaced with Ushiwakamaru. However, her class is also Berserker.
Ushiwakamaru's skills are very dangerous in the hands of the enemy. She has full access to her Evasion skill as well as a team-wide (!) NP gauge boost.
Therefore, try to get rid of her as soon as possible as she is a far bigger threat for new Masters. She only has 600k HP, and at this point, most Masters should have several copies of Golden Sumo and Hot Spring Under the Moon, she can thus be disposed of quickly with most set-ups.
Regardless, build a team to counter Kazakoemaru as Masters still need to chew through up to 6 million HP.
The green Oni is still the same:
Kazakoemaru’s skill is harmless. The NP gauge seal on his NP can be annoying though.
New Masters should try to drain Kazakoemaru’s NP bar or disable him once with a full NP bar. This will result in one less NP over 15 turns provided Ushiwakamaru does not charge his NP bar.
Fielding Berserker and Rider event Servants is ideal, but non-event Buster Riders will perform great against Kazakoemarua as well.
For new Masters who have been diligently raising Kintoki (Rider), he will do an immense amount of damage here with some additional beans.
Using the Bean consumables will speed up your runs immensely and helps to reduce any potential risks.
Once again Queen Medb is Kazakoemaru's worst nightmare.

Try to field set-ups with two Servants that provide offensive buffs for one main DPS with Golden Sumo equipped.
But new Masters should not 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.
If in doubt, the Chaldea Combat Uniform is a safe option. A heavily damaged Ushiwakamaru will likely cast her Evasion skill, consider stunning her if she can't be killed in one strong blow to prevent the Evasion from being cast.