This is a guide for the Re-human ending which ends with successfully creating the serum.
Check in at the reception.
Then go downstairs and ask for 3 sowl spirits and you will end up in your room.
To decipher A’s letter you’ll need 2 items.
An onion from the garden.
Massage oil from the 5th floor.
Go to the kitchen. Use the onion on the frying pan and get fried onion.
Put the fried onion in the basin here and then the massage oil. After the basin is filled with this weird onion oil, put the empty letter in and you can finally read it. The letter tells you to go to the 4th floor.
(Actually, I went to the 4th floor without deciphering the letter so I guess this isn’t necessary)
Spill the ink on the carpet.
Then go to 3rd floor’s laundry room and tell the maid about the carpet and she’ll get out of your way.
Once you are in Room 401, check the toy box in the upper-left corner and find the stone’s box.
Ask the kid on 5th floor did he steal your stone and he’ll give back the stone and suggest you to meet ‘IT’. Now you can go back to your room and call it a day.
Go back to the 4th floor and enter Room 402.
Talk to the statue and ask it to open the door. Answer “IT”, ‘Flow of time’ and ‘I’m barely sane’.
Go down the stairs and after you reach the end and check it and then you can turn back.
When get caught be the receptionist, choose ‘Y’all are crazy’.