"The physician must ... have two special objects in view with regard to disease, namely, to do good or to do no harm"
My own patients should be treated with great respect without doing harm onto him/her. It was my creed as a doctor, but not anymore given my current circumstance.
The darkness exists not through demons, but disease, coming from the parasitic Diabolos Tarot Cards that invades the host's body through his/her negative emotions and propagates throughout the body in an irreversible process, transmogrifying him/her into a monster, known as a Daemonia. The Daemonia does whatever he/she can to slaughter as much humans as possible through natural disasters or incidents.
The only people who can eliminate the Daemonia are female warriors of 22 bloodlines possessing supernatural powers from each card of the Major Arcana of the Elemental Tarot, formed in an international organization covering as a fortune-telling school known as Sephiro Fiore.
Normal people can also access the powers of the Elemental Tarot by citing a prayer to the cards causing their genes to be rewritten to access these abilities.
I was told that my father, Joseph Kuroyuki, an epidemiologist of the Centers for Disease Control from America, had also assisted this organization at times in investigating and eliminating the Daemonia.
Two of the users of the Elemental Tarot I'm already familiar with before I joined were Akari Taiyou, user of The Sun card and daughter (and successor) of Hinata Taiyou, whom my father befriended and fought alongside with; and Luna Tsukuyomi, user of The Moon card and daughter of the Tsukuyomi Zaibatsu where I was the family doctor for a while and whom I tutored at the same time when she was six.
It is my job to fully investigate, contain and/or even eliminate threats to the health of the public and that's why me and my father joined to fight this disease.
Didn't expect the conditions of this task to be.... horrid.
After the Daemonia strain has fully propagated, the Daemonia's host also serves as it's protective shell. Meaning there is no other solution to eliminate the Daemonia than to eliminate the host.
Akari was repulsed of this duty after the revelation of killing her first Daemonia who was her cousin, Fuyuna, someone that even I am close to. I, however, still continued fighting in spite of my repulsion towards this revelation that they hid even from me. However the organization (with harsh measures) refused to let her leave saying that they should strictly follow their "destiny".
A chance of resolve however, came to her after she suddenly discovered her peculiar ability to hear the thoughts of the infected and she realized that even though she can't save them, she can still carry on with their feelings.
But my observations of this ability concluded a much more important fact that myself and the entire organization should always know...
Their pain is the least to be taken lightly.
These people are trapped in their own darkness, constantly suffering from their inevitable functions.. That's why it is our honor to understand their pain with earnest sympathy and to release them before they harm any others
We must do this. Not because it's our destiny, not because we are told to do, but because...
It's the choice we both made.