hehe i solved it
guide under the cut!
There's a file ingame (no screenshot, sry) that says the blood of 115 infected was administered to a "Marie" a.k.a the Girl. We start the puzzle by going down to the care center basement and grind up 115 bodies.
I counted them, but you can also wait roughly 15 minutes. Since all the blood needs to be 'administered', you CANNOT kill any zombies in the grinder. I recommend shooting their kneecaps and kicking them into the grinder. If you did it right, the message after draining the blood is 'a ton of blood flowed out'. If you get 'a lot' instead, re-do it. After your elevator struggle with Marie, pick up her hand.
Take it to a microscope to analyse and you will get this message:
lovely. Now, do you remember this guy?
behind him, we can make out an '8'. Hence, we go to the Care Center bathroom and flush the toilet exactly 8 times. If you do this, you'll find this in the room with the exploding blood tank at the bottom of the stairs
Put this in the item box for now, it will stay there for any subsequent playthroughs. While playing as Leon, enter the basketball court after defeating the tyrant. There, you'll find a figure's head. Kick it into the fallen basketball hoop, and this pops up
After that, we return to Kendo's gun shop where the rest of the figure is. Interact with it to get this message
That makes our code GGC GUC GUG UCU. To find out what the symbols mean, go to the microscope in the East Wing Blood Lab in the Care Center to find an engraving:
Because I'm a space nerd, I know that that is roughly the distance between Earth and Sun, hence G = Sun. Now go to the Elevator room in the Courtyard. Take the hourglass that seemed useless in former playthroughs, unscrew it, and let the sand fall until you can read an engraving in the top
Once again, I know this because I love space, but that's roughly the distance between Earth and the moon, hence U = moon.
In the Grace Ashcroft's Blood Analysis Report, it says "C = 4.2 ly". 4.2 light years is the distance to Proxima Centauri, the star closest to Earth (after the sun) so C = star.
Fetch Marie's doll and Emily. I also grabbed Marie's severed hand because it enabled me to be able to interact, and head to the Lead Researcher's Office. There, input the code three at a time. If you did it correctly, you'll hear a creepy laugh and get the screen I showed above.
Or if you're lazy, just do the steps to obtain the doll and do the last step without all the hunting for the meaning of the letters. Have fun :)
