Solitary, gloomy, sadistic... Kind only to Randal
He speaks in a way that makes you uncomfortable; if you're not Randal, he'll treat you terribly.
The entity that once appeared in Randal's dreams thus became one of his best friends... Watching him grow and always accompanying him. Although... Randal is slowly forgetting him, and Satoru is starting to feel jealous of what he has now... like Sebastian's company.
