Oh this sounds interesting! But will there only be tora, juuichi and tatsuki? Im one of the Shin fanboys and i would really really love to see him back! I can imagine there could be a continuation after SPOILER AHEAD
the Kiss at the end from the original game when Hiro left with the Bus!
Maybe give a option in the beginning to choose which character you had your expiriences with in the original game and then go from there.
(I havent played your game yet)