Games like The Rainman
Games like The Rainman include Five Nights at Freddy's: Into the Pit, Poppy Playtime, Until Dawn™, That's not my Neighbor, and No, I'm not a Human. We matched them by the tags players give The Rainman on Steam (Singleplayer, Horror, 1980s, Adventure, and Mystery): closest matches first, and among equally close ones the better-known games.

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

Poppy Playtime
Shared: Singleplayer · Horror · Mystery

Until Dawn™
Shared: Horror · Singleplayer · Adventure

That's not my Neighbor
Shared: Adventure · Horror · Casual

No, I'm not a Human
Shared: Horror · Singleplayer · Choices Matter

The Casting of Frank Stone™
Shared: Horror · Singleplayer · Choices Matter

Firewatch
Shared: Adventure · Singleplayer · Mystery

Five Nights at Freddy's: Security Breach
Shared: Singleplayer · Horror · Adventure

Tiny Bunny
Shared: Horror · Singleplayer · Visual Novel

Urban Myth Dissolution Center
Shared: Singleplayer · Adventure · Mystery

Lay a Beauty to Rest: The Darkness Peach Blossom Spring
Shared: Adventure · Mystery · Singleplayer

Return to Shironagasu Island
Shared: Adventure · Horror · Mystery

Killer Frequency
Shared: Horror · Adventure · 1980s

Mirror 2: Project X
Shared: Singleplayer · Interactive Fiction · Visual Novel

The Wolf Among Us
Shared: Adventure · Choices Matter · Multiple Endings

Oxenfree
Shared: Choices Matter · Horror · Mystery

The Room
Shared: Singleplayer · Mystery · Adventure

Far Away
Shared: Singleplayer · Choices Matter · Visual Novel

The Test
Shared: Singleplayer · Multiple Endings · Horror

Firework
Shared: Horror · Singleplayer · Mystery

Florence
Shared: Adventure · Casual · Singleplayer

PARANORMASIGHT: The Seven Mysteries of Honjo
Shared: Horror · Adventure · Visual Novel

Danganronpa: Trigger Happy Havoc
Shared: Singleplayer · Mystery · Horror

Outer Wilds
Shared: Mystery · Adventure · Singleplayer