What an extremely sobering episode, from Aragaki’s PTSD from the war, to his abandonment issues with Nanbu, and Nanbu’s guilt for giving up on Aragaki. I’ve been wishing to know more about Nanbu’s history since three episodes ago, but this is a boat load of heavy stuff I didn’t expect.
A younger Aragaki loses his legs and scars much of his body during his deployment in the warzone. However, the one constant that seems to follow him around is the blue butterfly that Aragaki sees seemingly everywhere. In the middle of the desert, the butterfly flies on by. In the destroyed ruins of a building, the butterfly lands on the fingers of a deceased woman. Even as he discovers the hidden explosive, the butterfly flying upwards is the final thing he sees.
The question arises of what does the butterfly mean to Aragaki? Is it a symbol of life that has developed in his psyche as a result of the trauma he experienced throughout the war? Is it perhaps Aragaki’s memory of Nanbu? A being that draws him to danger and abandons him? Aragaki himself has it tattooed on his body, so it must have imprinted itself onto Aragaki’s mentality.
During the initial meeting of Nanbu and Aragaki, their conversation is played off as friendly. A far cry from the vibe of the ending of Episode 4, where he practically screamed antagonist through his behavior and entrance. 
However, Episode 5 takes a radically different approach, going as far as to changing the OST to a relaxing tune. It isn’t until Nanbu says, “Just like good times,” that Aragaki displays his first sign of discontent. The final shreds of friendliness are torn away as Aragaki decides that he wishes to destroy Joe, out of anger towards Nanbu for abandoning him for another. Aragaki specifies that Nanbu must pay his half of the debt for everything Aragaki lost, which could mean both his physical legs, and of course the mental trauma inflicted onto him through the war.
This raises the idea that Aragaki blames Nanbu for the loss of his legs, although I’m not entirely sure why. Nanbu seems to be oblivious as well, and doesn’t even realize that Aragaki has lost his legs until Sachio displays it on the television. This is where the idea of Nanbu somehow being connected to the butterfly comes up. The butterfly leading Aragaki towards the explosive is ultimately why Aragaki lost his legs, and in a later nightmare of Aragaki’s, the image of Nanbu grabs onto his legs as the explosion goes off. Both the butterfly and that image of Nanbu lead to Aragaki losing his legs, and ultimately leads to Aragaki blaming Nanbu.
Sachio shows Joe a presentation on Aragaki’s previous opponents, and it seems that Aragaki is particularly brutal. Perhaps a result of his anger towards Nanbu, something he’s been channeling into his Megalo Boxing?
The episode fleshes out Nanbu and Aragaki’s history even more through brief flashbacks, such as Aragaki as soon as he gets onto the military bus. The first thing that Aragaki does is pull out his picture with Nanbu, almost as one would for a lover. The two had a serious friendship, and Aragaki used the idea of returning to Nanbu’s Gym as a motivator of sorts through the war. One could only imagine his pain to lose both his legs, discover that Nanbu’s Gym was closed, and that Nanbu had taken on another student. Aragaki actually lost everything. Just exactly how much of this loss is Nanbu’s fault is cloudy, but Aragaki clearly pushes it onto Nanbu quite a lot.
It’s later revealed at the Veteran Affairs building that Aragaki’s final hope was returning to Nanbu, the one thought that drove Aragaki forward through the war. Nanbu defends himself by saying that he thought Aragaki was dead, but Nanbu never even bothered to double check. To Aragaki this is the ultimate betrayal, and he interprets Nanbu’s actions as abandoning him and then trying to forget him.
Perhaps the most surprising scene of the episode comes soon after the Veteran Affairs building, with a postwar Aragaki considering suicide. The room is a mess with trash scattered all over, and Aragaki is holding a pistol barrel into his mouth. He’s sweating, crying, he’s lost his way. 
He has no one to return to because Nanbu is gone and his screams of anguish are haunting. I absolutely love his character because in many ways, Aragaki could very easily be the protagonist of his own show. A boxer abandoned by his teacher once he goes off to war, only to return and challenge his master’s new student. That is Aragaki’s narrative, and it’s something one can genuinely root for.
Nanbu goes on to do something surprising, sitting alone in his van and confessing to the rosary that’s tied around the rearview mirror. He admits his mistakes, saying that he did try to bury the memory of Aragaki away for convenience. However, the next scene is the conversation between Joe and Aragaki, where Joe chooses to trust Nanbu because Nanbu trusted in him. Aragaki warns Joe that Nanbu will betray Joe when the times come, just like he betrayed Aragaki but being our classic Joe, he don’t care!
Another flashback towards the end of the episode reveals an aspect of Nanbu’s past that perhaps Aragaki doesn’t know. A despairing Nanbu who throws a table at his television, distraught over the supposed death of Aragaki.
Perhaps to Aragaki, Nanbu didn’t give a second thought and just moved on with his life. But the flashback reveals to us, the viewers, that Nanbu was heartbroken and began his descent into alcoholism.
The episode ends with the match between Joe and Aragaki beginning, and as expected, Joe gets absolutely hammered by the rank 17 fighter. I have no idea how Joe is going to get out of this one since the episode ends with the timer at 9 seconds, but it’s not looking good for Joe. Perhaps this matter is not one to be settled in the boxing ring between Joe and Aragaki, but rather outside of it between Nanbu and Aragaki. It is an internal conflict between the two after all.
