Games like Manivore
Games like Manivore include Mouthwashing, Outlast, Outlast 2, Poppy Playtime, and No, I'm not a Human. We matched them by the tags players give Manivore on Steam (Psychological Horror, Atmospheric, Realistic, Thriller, and Singleplayer): closest matches first, and among equally close ones the better-known games.

Mouthwashing
Shared: Psychological Horror · Atmospheric · Horror

Outlast
Shared: Atmospheric · Psychological Horror · Horror

Outlast 2
Shared: Psychological Horror · Horror · Atmospheric

Poppy Playtime
Shared: Singleplayer · Horror · Psychological Horror

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

SOMA
Shared: Psychological Horror · Atmospheric · Horror

Welcome to Kowloon
Shared: Atmospheric · Psychological Horror · Horror

Visage
Shared: Psychological Horror · Horror · Dark

Summer of '58
Shared: Atmospheric · Psychological Horror · Thriller

Subliminal
Shared: Psychological Horror · Realistic · Atmospheric

Layers of Fear (2016)
Shared: Psychological Horror · Atmospheric · Horror

MiSide
Shared: Psychological Horror · Atmospheric · Singleplayer

From The Darkness
Shared: Psychological Horror · Horror · Dark

Psalm 5:9-13
Shared: Psychological Horror · Horror · Atmospheric

Still Wakes the Deep
Shared: Psychological Horror · Horror · Atmospheric

Little Nightmares II
Shared: Singleplayer · Atmospheric · Psychological Horror

Ready or Not
Shared: Realistic · Singleplayer · Psychological Horror

Garten of Banban
Shared: Psychological Horror · Singleplayer · Horror

Amnesia: The Dark Descent
Shared: Psychological Horror · Atmospheric · Horror

Scorn
Shared: Atmospheric · Horror · Psychological Horror

Little Nightmares
Shared: Atmospheric · Horror · Singleplayer

Tiny Bunny
Shared: Atmospheric · Psychological Horror · Horror

Resident Evil 7 Biohazard
Shared: Horror · Singleplayer · Atmospheric

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