Thanks for playing and enjoying the game. We actually wanted to have more levels in the game, but ran out if time. That is why the story ends kind of abrupt with Izumi drinking the water. But we had to cut that, because we ran out of time to add the other levels. In hindsight, we should have made that clearer in the game.
The story was already fleshed out. It would have dealt with the consequences of Izumi drinking the water and how that changes Izumi, but also the relationship between the sisters.