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Go to detective Office and talk to the guy above he will tell you that you need to pay him 1000 coin to get Paper (Just don't Pay it and go to talk with ISA)

Before enter the building make sure you have enough pick lock and dispel scroll (Recommend dispel scroll 8-10  to destroy all crystal and unlock the door in building) now coin is important to buy all this if you don't have enough coin the only way (i don't know is it have another way?) is  play new game save and save coin as much as you can