Dark World: I Became the Doctor of Horrors

Ryan traveled to such a mysterious world and became an apprentice in a monster pharmacy.
[Ding! You cured Miss Succubus's androphobia, you got "Durable Potion Formula" x1, 500 Skull Coins, Miss Succubus's favorability +100]
[Ding! Your massage technique made the vampire princess feel physically and mentally happy, you got "Medical Skill: Eagle Vine Hand" x1, 500 Skull Coins, Vampire Princess's dependence +100]
Let's see how a human, in this dark world full of monsters and evil spirits worse than demons, step by step to the pinnacle of life.
"Sorry, all the monsters and horrors, if you want to kill me, please ask my patients if they agree first!"
But...
What's the truth behind this Dark World?
Is it a paradise for horrors demons and monsters
a prison for imprisoned criminals,?
or a shelter when the True Darkness comes?
Why Ryan traveled to here?
To find out all the truth, let's follow Ryan's footprint by reading this novel!