Sprout.

Let's start this way: Sprout is a serial killer, and Cosmo is his victim, whom he's already kidnapped. To survive, you need to be a sort of patient, and Sprout is a sort of doctor. This is your game, and there's even an abandoned hospital for this game.

You're one of the survivors. Yes, there were others, but they died. Some tried to escape, or didn't play the patient, or took the medicine. You can't swallow any medicine, including poison or drugs.

Sprout walked into Cosmo's room while he was drawing, yeah, Cosmo's trying to relieve stress or forget about fear.

— "Cosmo, what are you drawing? I came to check on you."