If I could tinker with the Mirei/Majima aspect of the story, I honestly wouldn't alter it that much but I really think if he had married her when they were both teenagers, she's the upcoming pop idol and he's the bad boy Yakuza and they fall hard and fast and it's 1982, they both grew up in an era where if you fall in love, you get married, that's just how it goes- so they get married much too quick and then it just all falls to pieces spectacularly, he leaves and that's that. I don't know, I think that would have worked, it would have added an extra layer to his and Saejima's plan as well, like Majima's just thinking I'm only 20 and I'm a fuck up in life, I'm already divorced, the only other person I have is this guy and he's intent on going out in a blaze of glory... so I'm happy to go down with him- because what's really the use of me?