Games like Opening Up
Games like Opening Up include Outlast, Layers of Fear (2016), Blair Witch, Still Wakes the Deep, and Escape the Backrooms. We matched them by the tags players give Opening Up on Steam (Adventure, Horror, Psychological Horror, First-Person, and Walking Simulator): closest matches first, and among equally close ones the better-known games.

Outlast
Shared: Horror · First-Person · Psychological Horror

Layers of Fear (2016)
Shared: Horror · Psychological Horror · First-Person

Blair Witch
Shared: Adventure · Horror · Psychological Horror

Still Wakes the Deep
Shared: Horror · Psychological Horror · First-Person

Escape the Backrooms
Shared: Horror · Psychological Horror · First-Person

Lethal Company
Shared: Horror · First-Person · Psychological Horror

Fears to Fathom® - Scratch Creek
Shared: Horror · Adventure · Psychological Horror

The Beast Inside
Shared: Adventure · Horror · First-Person

Fears to Fathom - Woodbury Getaway
Shared: Adventure · Psychological Horror · Horror

Firewatch
Shared: Adventure · Walking Simulator · First-Person

Amnesia: A Machine For Pigs
Shared: Horror · Walking Simulator · First-Person

Poppy Playtime
Shared: Horror · First-Person · Psychological Horror

Visage
Shared: Horror · Psychological Horror · First-Person

MiSide
Shared: Psychological Horror · Horror · First-Person

KARMA: The Dark World
Shared: Horror · Psychological Horror · Walking Simulator

The Park®
Shared: Horror · Psychological Horror · First-Person

SOMA
Shared: Horror · Psychological Horror · First-Person

The Cabin Factory
Shared: Horror · Psychological Horror · Walking Simulator

Fears to Fathom - Ironbark Lookout
Shared: Horror · Psychological Horror · Adventure

Phasmophobia
Shared: Horror · Psychological Horror · First-Person

Outlast 2
Shared: Horror · Psychological Horror · First-Person

Scanner Sombre
Shared: Horror · Adventure · Walking Simulator

What Remains of Edith Finch
Shared: Walking Simulator · Adventure · First-Person

Slender: The Arrival
Shared: Horror · First-Person · Psychological Horror