Re: Minato using sage mode is not a plote hole
Minato is really intelligent.
He created the Rasengan after seeing a tailed beast bomb once.
Having Jiraiya as his teacher and having a contract with the toads means he probably had Sage Mode explained to him, but never really got the chance to fully realize his potential with it. With all this dumbfounded standing around in shock, he probably began to feel the natural energy around him, and it clicked.
Naruto completed his Rasenshuriken mid-battle (but perfected it later) so why couldn't the man who created Rasengan figure out Sage Mode?
Either way, it doesn't matter, and for some stupid reason, Kishi had Minato practically charge straight at Madara instead of formulating a real plan, so he got *****slapped.