Yo Apex...I think Obito from his blindspot was able to react to 5G Gai because he had shared vision with his Jinchuurikis
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(Rinnegan) If Mu attacks without him being able to see Mu, it would most likely be a different case.
Though I'd admit Mu would only be able to succeed with this due to invisibility because even Obito reacted to V1 Ay with Kamui
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If Mu attacks him head on, he'd react. Then again Mu can still react to Obito giving the fact that he's a sensor and Fu could react to Obito from his blind spot
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and we know Mu has much better reactions since he could react to something the Raikage failed to react to here
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