Games like Yume Nikki
Games like Yume Nikki include Mouthwashing, DISTRAINT: Deluxe Edition, Poppy Playtime, Layers of Fear (2016), and Layers of Fear 2 (2019). We matched them by the tags players give Yume Nikki on Steam (Indie, Psychological Horror, Free to Play, Surreal, and Pixel Graphics): closest matches first, and among equally close ones the better-known games.

Mouthwashing
Shared: Psychological Horror · Indie · Horror

DISTRAINT: Deluxe Edition
Shared: Indie · Psychological Horror · Pixel Graphics

Poppy Playtime
Shared: Free to Play · Horror · Psychological Horror

Layers of Fear (2016)
Shared: Psychological Horror · Indie · Horror

Layers of Fear 2 (2019)
Shared: Psychological Horror · Indie · Horror

OMORI
Shared: Psychological Horror · Indie · Pixel Graphics

What Remains of Edith Finch
Shared: Walking Simulator · Atmospheric · Exploration

Fran Bow
Shared: Psychological Horror · Indie · Horror

OneShot
Shared: Indie · Pixel Graphics · Atmospheric

Endacopia
Shared: Psychological Horror · Surreal · Pixel Graphics

The Cat Lady
Shared: Psychological Horror · Indie · Horror

Samsara Room
Shared: Indie · Free to Play · Psychological Horror

SOMA
Shared: Psychological Horror · Horror · Atmospheric

Mad Father
Shared: Psychological Horror · Pixel Graphics · Horror

[Chillas Art] The Convenience Store
Shared: Indie · Psychological Horror · Horror

Ib
Shared: Indie · Pixel Graphics · Psychological Horror

INMOST
Shared: Indie · Pixel Graphics · Exploration

IMSCARED
Shared: Indie · Psychological Horror · Pixel Graphics

Detention
Shared: Indie · Psychological Horror · Horror

Visage
Shared: Psychological Horror · Horror · Indie

Eclipsium
Shared: Psychological Horror · Surreal · Walking Simulator

Milk outside a bag of milk outside a bag of milk
Shared: Psychological Horror · Indie · Pixel Graphics

DISTRAINT 2
Shared: Psychological Horror · Horror · Atmospheric

No, I'm not a Human
Shared: Psychological Horror · Indie · Horror