There must be a downside to Shinsuusenju

[FemmeFatale]

IT's strength is it weakness.
Like 100% Katsuyu

 

[AGoodBoy]

Nah, I don't think that would be the reason. He and madara are fighting a big distance away from the allience.

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This should fit.

The distance is irrelevant. It crossed 5 kyuubi distances in a few steps. The statue alone would be 5x(without the shield of 1000 hands) the size of those entities in that pic. You can already see how big that is. He wouldn't be able to see SA, and with those 1k earth changing punches, he could easily kill thousands of people in the crossfire. And, to do what? moderately damage Perfect Susano'o? What's the point in that? Madara would be unphased, half of SA would be dead, and the PS he partially destroyed would be reformed... Shinshuu has no use apart from removing a Perfect susano'o coat to knock kyuubi out. Any other application madara can simply reform PS.

 

[deva pein]

IT's strength is it weakness.
Like 100% Katsuyu

Except Katsuyu can only heal fodders. Shinsuusenju is the only thing that can damage and remove PS.
Katsuyu is a fodder summon.

 

[Shura]

Size isn't a factor. When Obito put up the barrier they had plenty

This. ^ If Master says so then it is so. End of story.