Hidden throughout the Niwa Hotel and it's grounds are collectibles which will give you hints as to what really happened. In order to fully understand the story you need to each of them. Collecting them all will also enable you to unlock the An Unknown Outcome, Followed the Trail, Calling Out to Me, All That's Left Unsaid, Devouring Darkness, and Puzzling Out the Past achievements. Take a look at the video below to see the location of each of the collectibles in The Medium.
Echoes, Notes, Diaries, and Postcards Locations
Famished Feline Achievement - 0:27��?
Photo 1: Jack - 0:54��?
Postcard: Niwa Says Hello - 1:12��?
Eerie Drawing: Someone New - 1:33��?
Echo 1 - 2:00��?
Postcard: Honest Work - 2:38��?
Echo 2 - 3:12��?
Postcard: Promotion - 3:35��?
Echo 3 - 3:59��?
Memory Shard 1 - 4:40��?
Echo 4 - 5:30��?
Mentor's Diary: An Apology - 5:30��?
Memory Shard 2 - 6:12��?
Echo 5 - 6:43��?
Eerie Drawing: Lonely - 7:03��?
Troubled Man's Notes: A Peaceful Place - 7:30��?
Eerie Drawing: Old Man - 7:30��?
Troubled Man's Note: To-Do List - 8:05��?
Troubled Man's Note: Getting Stronger - 8:35��?
Photo 2: From Hiding - 8:35��?
Troubled Man's Note: Fever Dreams - 9:02��?
Echo 6 - 9:24��?
Echo 7 - 9:53��?
Echo 8 - 10:13��?
Postcard: Someday - 10:36��?
Troubled Man's Note: Good Old Frank - 10:51��?
Echo 9 - 11:11��?
Echo 10 - 11:39��?
Echo 11 - 12:02��?
Echo 12 - 12:32��?
Other: Torn Illustration - 13:11��?
Echo 13 - 14:11��?
Eerie Drawing: Bad Nursie - 14:41��?
Eerie Drawing: Dark - 14:59��? (Split Path: Male Soul)
Echo 14 - 15:23��? (Split Path: Male Soul)
Echo 15 - 15:49��? (Split Path: Male Soul)
Postcard: A Scenic View - 16:25��? (Split Path: Female Soul)
Echo 16 - 17:15��? (Split Path: Female Soul)
Echo 17, 18, 19, 20 - 17:45..