Have you noticed the description of team instance? It says "There is a small chance of an Elite ninja showing up after the battle"!

I have met the elite ninjas several times and want to share them XD

The first elite ninja I met is Kinkaku, but I was really suprised at that moment and didn't have enough time to take a screenshot coz the elite ninja is not strong at all

And for the following three times, I met white wolf once and fukurokumaru twice

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And the rewards:

If you meet other elite ninjas, please share them