Crows: The Man Who Climbed to the Top, Starting from Suzuran

There was once a legendary organization called MUGEN that controlled this neighborhood. Their overwhelming power allowed them to rule the area. But the Amamiya brothers refused to submit to MUGEN, and the two of them alone managed to match the organization blow for blow. In the end, neither side could claim victory. Then, after a certain incident, MUGEN suddenly disbanded, and the Amamiya brothers disappeared without a trace. (All characters are adults. The story will also involve High & Low, so character power levels will be adjusted slightly, but not too much. It will draw on both the films and the manga, with some changes to the story. Many events will happen earlier. If you have any questions or concerns while reading, feel free to bring them up, and I'll explain when I see them. Even if you haven't seen the original, that's fine. I'll lay out the whole story clearly, so you can enjoy it in comfort.)