from what we know its a sequel that follows the neutral route from the 1st game
As far as i understand, after playing this demo version, at the very beginning of the game it will be possible to choose a neutral route or a continuation with characters of the first part.
If the player chose to continue the story of characters original game, then we will be shown the future of Ryoka with different men (depending on the chosen route).
If the player chooses a neutral route, then most likely a new character (on pic - man on train station) will be involved in this route.
p.s. of course, this is just my theory, but i made it based on the character selection menu of the previous game in preview version.