why was the real Nishi so willing to help Mifune's character? he not only swaps identities to help him out, but is his accomplice throughout his entire mission.
they give a brief background about how they knew each other in the past, but did I miss the reason their bond was so thick? its a hell of a risk for the guy to take
If I'm not wrong - they were friends since kids and stuck together through some hard times... so basically that's the bond, I don't find anything stange in it.
They did mention in the film that his family from the north were killed in a naval bombardment. So it's safe to assume like the fake Koichi Nishi/Itakura character, both had nothing to lose anymore.
They were close friends who had grown up together under real hardship during and after the war. Not just ordinary childhood friends, as i'll point out since you scoffed at the notion that one friend would never go so far for another. These two people had already done illegal and dangerous things to survive. Plus, elsewhere on this thread someone pointed out that Real Nishi had nothing to lose anyway. Not-Real Nishi's father was essentially murdered and the men responsible for his death would never face justice, and Real Nishi seemed to share Not-Real Nishi's disgust for the corruption and injustice of the system, so it's not hard to see why Real Nishi, who had nothing to lose anyway, agreed to help his friend in his quest to achieve justice in his own way.
"The people, and the people alone, are the motive force in the making of world history." Mao
Additionally, Itakura was effectively a silent partner in that he was unknown to the evil empire thus enabling him to be an ideal accomplice, able to move quietly in the background. Heck, they were virtually family and shared a deep love and respect. In a word, loyalty. I'm not surprised anyone questions this, but hey, have a heart!
Indeed. The two had also defended the munitions factory too, at the end of the WWII, from what I can tell. They were very close, old friends, and had lived through perilous situations together before.