Isamu dying would have served no purpose, unless you just didn't like the guy and were happy to see him get greased. Isamu was cold, irresponsible, and his braggadocio made Kakizaki look humble, so he's a pretty hard guy to like. They never explain why he has that strange moment before death thing do they?.
Guld while being very honorable on the surface was a hair's breadth away from being a murderer, and already was a rapist. Guld had to die at the end to redeem himself for his acts. Yeah, it would have been nice to see them all friends again, but realistically, that never would have happened. I still don't understand why Myung hooked up with Guld considering what he had done to her in the past, I guess the "poor zentraedi" defense really carries alot of weight .
Interesting to see how many people assume that Isamu and Myung end up together at the end of the story aside from just still being acquaintances or friends. Let's face it, Myung has some serious issues, she's pissed at the world, and pissed at Isamu because he gets to do what he loves, and she doesn't. Additionally, she obviously has some intimacy issues, having really picked the wrong dude to have sex with. . And I don't see Isamu settling down just because of this incident.