Games like The Window 8:Millennium
Games like The Window 8:Millennium include KinitoPET, Firework, OMORI, Poppy Playtime, and DISTRAINT: Deluxe Edition. We matched them by the tags players give The Window 8:Millennium on Steam (Adventure, Psychological Horror, Horror, 2D, and Immersive Sim): closest matches first, and among equally close ones the better-known games.

KinitoPET
Shared: Psychological Horror · Horror · 2D

Firework
Shared: Horror · 2D · Psychological Horror

OMORI
Shared: Psychological Horror · Horror · Indie

Poppy Playtime
Shared: Horror · Psychological Horror · Adventure

DISTRAINT: Deluxe Edition
Shared: Psychological Horror · Horror · Adventure

Sally Face - Episode One
Shared: Psychological Horror · Horror · Adventure

MiSide
Shared: Psychological Horror · Horror · Adventure

Platform 8
Shared: Adventure · Psychological Horror · Hidden Object

Little Nightmares II
Shared: Adventure · Horror · Psychological Horror

Rusty Lake Paradise
Shared: Adventure · Psychological Horror · Horror

Fran Bow
Shared: Psychological Horror · Adventure · Horror

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

Five Nights at Freddy's: Into the Pit
Shared: Adventure · Horror · 2D

Mad Father
Shared: Psychological Horror · Horror · 2D

Lobotomy Corporation | Monster Management Simulation
Shared: Psychological Horror · Horror · Simulation

DREDGE
Shared: Adventure · Exploration · Psychological Horror

Escape the Backrooms
Shared: Horror · Psychological Horror · Adventure

SOMA
Shared: Psychological Horror · Horror · Exploration

Little Nightmares
Shared: Adventure · Horror · Psychological Horror

Outlast
Shared: Horror · Psychological Horror · Adventure

SILENT HILL 2
Shared: Psychological Horror · Horror · Adventure

[Chillas Art] Parasocial
Shared: Psychological Horror · Horror · Immersive Sim

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

Mouthwashing
Shared: Psychological Horror · Horror · Indie