What about these hand signs?

[sacmador]

Before using death reaper soul technique, Minato is using hand signs and the third understands that Minato is using DRS by seeing these hand signs.

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We see there Orochimaru whose arms are bitten by demon can use death reaper soul.

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[PredictionGuru]

Simple; Oro > Minato

 

[MySusanooIsPurple]

Simple; Oro > Minato

i disagree

 

[Frankenstein]

He is wearing a strange mask if you noticed though

 

[PredictionGuru]

Simple; Oro > Minato

Ok, you have a right to disagree

 

[thegame]

Oro isn't using the death reaper sealing technique, he was using some mask, which apparently was the source of the death reaper or something like that. So it would be different seals, else Oro should had been sealed inside the death reaper too.

 

[Aertes]

Minato used death reaper to seal Kurama.
Oro just called the shinigami and get possessed by it.It's not stated that this is a jutsu.
Two totally different things.