The woman at the restaurant...
...that Nishi visits and sends packages to - is she the widow of his dead partner, or the wife who left his crippled partner? Her scenes were so short, and there was almost no dialogue, I wasn't sure...
Also, I don't understand why he feels so guilty for either of the things that befell his partners. I understand wishing you could've done more, but what did he NOT do that should make him, specifically, feel so guilty? Especially the second guy who ends up crippled. How did that have anything to do with him? I have a hunch the subtitles on my copy might have left some things out.