Steps :

Preparation :

Iruka must have the lowest Life, take down his Life Magatama if you have to.

Put Iruka last, so he would shield everything.

R1 : Mei's poison must not kill the puppet, so she would be chaos'ed. Would be very helpful if she hit only other ninja, and not Ao's bunshin, ESPECIALLY Chojuro. Wait until Ao use his mystery on Iruka, then use Sasuke barrier.

R2 : Mei would 'hit' on Iruka, killing him, or not. Lightning mystery & Fu's on Mei, make sure she got chaos.

R3 : Mei in chaos, she can't use her mystery. Depend on RNG, Sasuke might be able to use his mystery, focus on killing Mei.

Done.

Hints : Lightning Main is your damage dealer, meld your attack magatama on him if your attack is not strong enough.

Resistance is important in Iruka, and Defense on Iruka and Fu.

It might take several try or more.

Comparison : In my playthrough, in round 1, Mei hit on Chojuro and Sakura. Lightning killed 2 bunshin & Chojuro. Round 2, Iruka survived, PB Sasuke use his mystery, Lighitning killed PB Sasuke & Sakura. By the end of round 3, Mei is dead, with only Ao left, while I have Sasuke, Lightning & Fu.