Why Did Tobirama develop the Edo Tensei?

[Hakuteiken]

I didn't notice him bein that confident though. He probably knew, and Tobirama could have known as well. But this is weird, then. If he knew about it, then that means it has happened before. Maybe this is why Tobirama didn't use Edo Tensei again.

How would the ones that are summoned know the seals, though?
Besides, this time, Tobirama was moving freely for a while, unlike the first time he was summoned, yet, he didn't break free of the jutsu again. This is inexplicable if he knows this reality.

[M3J]

Scroll? Someone Tobirama trusted taught them that? It's all weird anyway though.

Could be that you can't use the seals to keep yourself bound to the world until the caster stops Edo TEnsei.

[Zancrow]

Theres one guy who discovered how to stop edo tensai and hes not even from naruto !!

[Hakuteiken]

Could be that you can't use the seals to keep yourself bound to the world until the caster stops Edo TEnsei.

That's the only option I find rather plausible.

[Notak]

Hashirama might have been able to break free of the ET before, like he can now. Unless that's related to the sacrifice being White Zetsu.

Assuming he could break free of it, he would whoop his brother's ass for summoning him. He could literally force him to unsummon him. Not to mention their brotherly love.

And Tobirama's reputation and integrity would be at risk as others said before

[okaneman]

maybe he wanna use ET to reviving his b*tches.. or his wife? or his bro Hashi..