There are 28 Memories to be collected throughout the various locations in the dream world. Once obtained, they will be displayed in the Memory Room and appear as a yellow square in the save menu. Each dot/square represents one memory.
Additionally, there are 7 items called Empties that are hidden throughout the dream world, typically found through invisible pathways or unorthodox solutions. Unlike Memories, they will not be displayed in the Memory Room and instead appear as an extra row of black squares with purple borders on the save menu. Each Empty has a brief effect on Muma's appearance when collected before returning her to the Memory Room.
Appearance: A wriggling piece of chewed-up bubblegum.
Location: Found in the Memory Room during the game's tutorial.
Appearance: A red rose swaying from side to side.
Location: Found in First Steps near a black rabbit, slightly southeast of the Memory Room doorway.
Appearance: A hovering white square with a smaller black square inside of it.
Location: Found in White Shores in front of a door leading back to the Memory Room.
Appearance: A piece of bright red red coral.
Location: Found in the Undersea Expanse by riding the fish northwest of the ladder leading to White Shores.
Appearance: A purple and red striped umbrella with a red handle.
Location: Found in Rainforest Road by going through the gap in the fence and then heading left, down, right, down, and then heading right on the second road. Muma will always appear with the Umbrella equipped when entering the Rainforest Road after it is obtained.
Appearance: A red soda can with a white stripe down its side and OK written on it. If the OK Lemon poster has been viewed in Chicago, then the soda can will be yellow.
Location: Found in the Swimming Pool vending machine. Can only be obtained by first swimming in the pool, grabbing the gray coin from one of the lockers, and then operating the vending machine with the gray coin.
Appearance: A snowglobe featuring a miniature brown house with a red roof depicted inside.
Location: Found in Pink Snowscape, located directly north of the igloo from Rainforest Road.
Appearance: A white and blue striped beach ball.
Location: Found in one of the houses in Red Sands B, being played with by a small girl. Interacting with the girl will make her disappear, letting the memory be obtained.
Appearance: A cassette tape dripping with blood.
Location: Found in the Occult Basement in the middle of a pentagram after crushing the five hearts scattered around the basement.
Appearance: A red balloon.
Location: Found on the top floor of the Monochrome Building, attached to the balcony.
Appearance: A silver, pixel art-styled sword with a golden hilt.
Location: Found in the Unicorn Woods after operating the arcade machine with a gray coin. Muma will always have the Sword equipped when she enters the Unicorn Woods after obtaining it. Allows her to slay the unicorn head enemies that appear in the world.
Appearance: A shiny, brown, pixel art-styled boot with pink wings.
Location: Found within one of the southern rooms in the Cave Game near a face made of blocks. Gives Muma the ability to double jump in the Cave of Perils, making traversing some parts much easier.
Appearance: A realistic pulsating heart.
Location: Found on a heart-shaped formation in Flesh n' Blood.
Appearance: A half moon and sun.
Location: Found on a pedestal in Windy Canyon. To remove the rocks blocking the pedestal, interact with the sun pedestal north of the entrance from the Dark Stairways, and then solve the puzzle in the moon cave.
Appearance: A white carrot.
Location: Found during summer inside the house's basement in the Isle of Seasons after feeding the rabbit and replanting the seeds.
Appearance: A yellow pixel overlapping a purple-red pixel.
Location: Found in a small room in Micro World, by taking the staircase in the side of one of the stack of cubes.
Appearance: A heart rapidly changing colors.
Location: Found in the Neon Zone by taking the rainbow teleporter in the second section while the area is blue. Each time you teleport, the area alternates between two sections, and the colors change through a cycle. You need to continue teleporting until the conditions are met to activate the rainbow teleporter.
Appearance: A wooden flute.
Location: Found in the Owl Swamp on an island after activating the musical owls.
Appearance: A white glove.
Location: Found in the Puzzle Chamber after solving the main puzzle.
Appearance: A swaying orange leaf.
Location: Found in the Glowing Meadow in the middle of a patch of glowing grass.
Appearance: A black egg with one eye.
Location: Found in the Lower Totem Hill.
Appearance: A small hourglass.
Location: Found atop a tall black pillar in the Sands of Time. To reach the hourglass, stand by the pillar until the sand buries it.
Appearance: A large shiny diamond.
Location: Found by breaking the glass in the back of the Swimming Pool and jumping into the newly opened hole.
Appearance: A wriggling purple ectoplasm.
Location: Found at the end of the passageway down the Stare's Stairs by interacting with the sitting Muma.
Appearance: A knife dripping with blood.
Location: Found in the Yin Lake section of Yin Yang Lake.
Appearance: A dice with different colors on each side.
Location: Found on the final floor of the R-Maze.
Appearance: A wand with a star.
Location: Found on the Moon.
Appearance: A tricolored bowtie.
Location: Found in the red section of the Realm of the Orb.
Memory Room's Empty
Effect: Static is flashed over Muma's body before she turns to face her hanged self.
Realm of the Orb's Empty
Effect: Muma is turned into a silhouette before pieces of her are scattered into the air, shriveling her away.
Blood n' Blood's Empty
Effect: Muma becomes completely red before she explodes into a mess of flesh and blood, her clothes falling to the ground.
Above the Clouds' Empty
Effect: Rainbows pour out of Muma's eyes, suddenly shaking violently before two more streams burst from her sides.
Retro Dungeon's Empty
Effect: Muma's appearance flickers between being her normal self and a white outline, then glitches into two copies of herself in different states.
Monochrome Building's Empty
Effect: Muma's eyes transform into a large red ovular pair with black scelera. Japanese あ symbols quickly shake around her as she screams.
Faraway Place's Empty
Effect: A hole forms in the middle of Muma's torso, from which black tendrils appear and completely engulf her.
A visual guide showing the location of all 28 memories as well as the 28 collectible coins.
This guide demonstrates how to obtain the 7 "empties" and the ending associated with these collectables.