What does the Hearts do in the Ego Terminal? And is it Possible too Fill them up?
In the future, unlocking the hearts will unlock events and more escape scenarios. Also, the events that require more hearts are more lewd.
In the pre-alpha demo such events are not yet implemented. It is possible to slightly raise the value, but not enough to fill even the first heart. Events that will raise the value faster are planned for future parts of the game.