Games like The Underpass
Games like The Underpass include The Exit 8, Platform 8, What Remains of Edith Finch, Firewatch, and Outer Wilds. We matched them by the tags players give The Underpass on Steam (Adventure, Simulation, Puzzle, Walking Simulator, and Exploration): closest matches first, and among equally close ones the better-known games.

The Exit 8
Shared: Puzzle · Exploration · Walking Simulator

Platform 8
Shared: Adventure · Simulation · Walking Simulator

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

Firewatch
Shared: Adventure · Walking Simulator · Atmospheric

Outer Wilds
Shared: Adventure · Exploration · Puzzle

INFRA
Shared: Puzzle · Exploration · Adventure

The Witness
Shared: Puzzle · Exploration · First-Person

Riven
Shared: Adventure · Puzzle · Exploration

Scanner Sombre
Shared: Walking Simulator · Adventure · Exploration

Quern - Undying Thoughts
Shared: Adventure · Puzzle · Exploration

Blue Prince
Shared: Puzzle · Exploration · Adventure

POOLS
Shared: Walking Simulator · Exploration · Realistic

Obduction
Shared: Adventure · Puzzle · Exploration

SnowRunner
Shared: Simulation · Adventure · Exploration

Killer Frequency
Shared: Adventure · Puzzle · Simulation

Internet Cafe Simulator 2
Shared: Simulation · Exploration · 3D

The Long Dark
Shared: Exploration · Adventure · Simulation

The Cabin Factory
Shared: Walking Simulator · Adventure · Immersive Sim

Who's at the door?
Shared: Adventure · Simulation · Walking Simulator

NaissanceE
Shared: Exploration · Adventure · Walking Simulator

Bright Lights of Svetlov
Shared: Walking Simulator · Adventure · Exploration

Layers of Fear (2016)
Shared: Walking Simulator · Adventure · First-Person

MOLE
Shared: Simulation · Adventure · Puzzle

Millennium Dream
Shared: Adventure · Walking Simulator · Exploration