Debris (also occasionally known as Debris Dream) is a game made by Harinezumi (ハリネズミ). It involves an idiot (according to their description in the game's menu) Tatsuki (たつき) going to the dream world by sleeping. There is an extra playable portion as an unlockable character in the post-game. It also seems to have glass and glitch motifs, possibly relating to the title of "Debris": scattered remains of trash or wreckage.
Like most Yume Nikki fangames, Tatsuki refuses to leave their room, but has a balcony and video game console with a game called Yoke. Tatsuki saves in what appears to be a diary or journal, and enters the dream world by sleeping in their bed.
Even though Debris stays true to the nature of Yume Nikki Fangames, it adds a few new things such as having locked doors in the nexus, and is known for its many events and attention to detail.
Debris starts out like most fangames, but focuses heavily on events and the environment to explain Tatsuki and their possible personality/past. After collecting all the effects, there is an extra playable portion as Lefia for the other two endings. Debris can end in four ways, only one being the "True END" (explained in detail on the walkthrough page).
Tatsuki holds a pair of scissors as a weapon. Pressing Shift makes Tatsuki snip the scissors twice.
Tatsuki turns upside-down. Pressing Shift makes them spin in a circle. When spinning, some NPCs may look different for a short amount of time, and it can be used to activate some events.
Tatsuki turns into a mouse, increasing their speed. Pressing Shift makes them alternate between a human and a mouse.
Tatsuki gains a pan on their head with a pot lid as their shield. Pressing Shift makes them adjust the hat.
Tuxedo / Formal Wear (れいふく)
Tatsuki wears a tuxedo. Pressing Shift makes them bow.
Tatsuki becomes a black wolf-like monster with yellow eyes. Pressing Shift makes them roar, causing NPCs to scatter and run away from Tatsuki in a panic.
Hand Mirror (てかがみ)
Tatsuki holds a hand mirror. Pressing Shift makes them raise the mirror, stopping NPCs and chasers from moving.
Tatsuki carries a bidoro (Japanese glass flute/toy) and plays it when Shift is pressed. There is a rare chance that Tatsuki will blow too hard on the bidoro and break it, making it unusable until you wake up.
Tatsuki's face becomes an empty hole, along with gaining a pink shirt and green hair. Pressing Shift makes them stretch their face and return to the nexus.
Desk Lamp (あかり)
Tatsuki holds a desk lamp. Pressing Shift turns the lamp on or off.
Tatsuki becomes made of rock. Pressing SHIFT makes a small rock fall from their head, and it stays on the screen (can be used as a marker) until it is picked up again by interacting with it. Only one small rock can be on the screen at a time, and after exiting the area or room, it goes away.
Tatsuki becomes slime, slowing them down. Pressing Shift makes them wiggle.
Tatsuki turns into a card. Pressing Shift makes the card change suits.
Tatsuki carries a small gong. Pressing Shift makes it rain, pressing it again makes it stop raining. If Tatsuki wakes up while this effect is on, then instead of pinching their cheek, they will hit the gong.
Tatsuki becomes made of blue glass. Pressing Shift makes them shatter or become whole again. When shattered, Tatsuki cannot move.
Tatsuki's eyes are missing with lots of blood in the sockets, causing them to walk in random directions when not controlled. Pressing Shift makes them clean the blood.
Arm Clock (うでどけい)
Tatsuki's head becomes a clock with arms for pointers in the face and loses their own arms. Pressing Shift makes the pointer spin.
The second playable character, an unlockable protagonist. Lefia is a princess with long blonde hair, a crown and a big pink gown.
Headless Girl (首無し)
Acts as the game's chaser. A girl with black hair tied in twintails who wears a yellow school uniform/dress with a bluish neckerchief. Normally she is not active. When she turns into a chaser, her head is cut off and she turns into a headless, completely black figure. Alternatively, her head in an all-black form can act as a chaser.
Rose Princess / Barahime (薔薇姫)
A girl in purple, dressed like a princess. She has very long purple hair, and wears a hat with a flower on her head. If you interact with her or interact with the cute animals in the same room with her, she will smile at you. However, if you interact too often with her...
Coffee Child (コーヒー子)
A child with light brown hair who carries a coffee cup their head. They give Tatsuki a cup of coffee when interacted with. They have an extreme reaction to one of the effects.
Anna and Anno
Two girls standing side-by-side in a room at the back of the underwater map. The one on the left wears yellow clothes. The one on the right has twintails and red clothes. These girls react to a certain effect.
A light blue-haired girl who wears blue clothes, has green eyes and wears green shoes.
A faceless boy with teal hair and purple skin who wears a blue shirt, beige pants and a pair of shoes that match his hair color.
Blue Drooling Figure
A bluish-teal-colored figure sitting on the bench in the vending machines room.
A monochrome child (presumably male) with short, pitch black hair, white/light grey eyes, wears a grey-scale outfit.