Games like Red Line
Games like Red Line include Firework, Unheard - Voices of Crime, Tales of the Black Forest, Angels of Death, and OMORI. We matched them by the tags players give Red Line on Steam (RPG, Puzzle, Mystery, Thriller, and Psychological Horror): closest matches first, and among equally close ones the better-known games.

Firework
Shared: Puzzle · Horror · Mystery

Unheard - Voices of Crime
Shared: Thriller · Mystery · Puzzle

Tales of the Black Forest
Shared: RPG · Pixel Graphics · Horror

Angels of Death
Shared: Puzzle · RPG · Horror

OMORI
Shared: Psychological Horror · RPG · Pixel Graphics

The Witch's House MV
Shared: RPG · Horror · Pixel Graphics

Sally Face - Episode One
Shared: Psychological Horror · Puzzle · Horror

Poppy Playtime
Shared: Puzzle · Horror · Mystery

Ib
Shared: Horror · Pixel Graphics · RPG

The Rewinder
Shared: Mystery · Puzzle · Pixel Graphics

Cat in the Box
Shared: Mystery · Horror · Psychological Horror

Sanfu
Shared: RPG · Mystery · Puzzle

The Room Two
Shared: Puzzle · Mystery · Horror

Paper Bride
Shared: Puzzle · Mystery · Horror

DISTRAINT: Deluxe Edition
Shared: Psychological Horror · Horror · Pixel Graphics

Cube Escape Collection
Shared: Puzzle · Mystery · Psychological Horror

CrossCode
Shared: RPG · Puzzle · Pixel Graphics

Cyber Manhunt
Shared: RPG · Puzzle · Mystery

Rusty Lake Paradise
Shared: Puzzle · Psychological Horror · Horror

The Case of the Golden Idol
Shared: Mystery · Puzzle · Thriller

The Hex
Shared: Mystery · Psychological Horror · Pixel Graphics

MiSide
Shared: Psychological Horror · Horror · Thriller

Fran Bow
Shared: Puzzle · Psychological Horror · Horror

Danganronpa V3: Killing Harmony
Shared: Mystery · Female Protagonist · Psychological Horror