Games like Parasite Tunnel
Games like Parasite Tunnel include Layers of Fear (2016), Firewatch, Outlast, Visage, and What Remains of Edith Finch. We matched them by the tags players give Parasite Tunnel on Steam (Walking Simulator, Adventure, Simulation, Psychological Horror, and Horror): closest matches first, and among equally close ones the better-known games.

Layers of Fear (2016)
Shared: Walking Simulator · Psychological Horror · Horror

Firewatch
Shared: Adventure · Walking Simulator · Atmospheric

Outlast
Shared: Horror · Psychological Horror · First-Person

Visage
Shared: Psychological Horror · Horror · Adventure

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

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

MiSide
Shared: Psychological Horror · Horror · Singleplayer

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

Ready or Not
Shared: Realistic · Singleplayer · Horror

Blair Witch
Shared: Adventure · Horror · Psychological Horror

Poppy Playtime
Shared: Horror · Singleplayer · Psychological Horror

Scanner Sombre
Shared: Walking Simulator · Adventure · Horror

Still Wakes the Deep
Shared: Psychological Horror · Horror · Walking Simulator

POOLS
Shared: Walking Simulator · Psychological Horror · Realistic

Welcome to Kowloon
Shared: Adventure · Walking Simulator · Horror

Amnesia: A Machine For Pigs
Shared: Walking Simulator · Horror · Psychological Horror

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

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

Among the Sleep - Enhanced Edition
Shared: Adventure · Horror · Walking Simulator

Five Nights at Freddy's
Shared: Horror · Psychological Horror · Singleplayer

Mouthwashing
Shared: Psychological Horror · Horror · Walking Simulator

Little Nightmares
Shared: Adventure · Horror · Singleplayer

The Death | Thần Trùng
Shared: Psychological Horror · Horror · Adventure

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