You could probably just release more small little "demos" like this, but each one centered around a different character.
In my mind, I'm sort of imagining it like how manga usually release in "volumes" and then when the manga is complete, there is a "box set" released that bundles them all into a neat single package.
So basically, make each character like their own "chapter/level" that you see from their perspective, and then at some point combine them all into one "game" that have a menu screen after the title that lets you choose the "chapter" so the player can piece the overall story together in whatever way they want.
EDIT: Also wanted to say that I'm really invested in these characters, even though I've literally only seen one of them so far, hahaha. The writing is really good and fun. Great work!