Games like Bittersweet Birthday
Games like Bittersweet Birthday include Impostor Factory, DELTARUNE, Titan Souls, Finding Paradise, and OMORI. We matched them by the tags players give Bittersweet Birthday on Steam (Souls-like, Pixel Graphics, Boss Rush, 2D, and Story Rich): closest matches first, and among equally close ones the better-known games.

Impostor Factory
Shared: Pixel Graphics · Story Rich · 2D

DELTARUNE
Shared: Pixel Graphics · Story Rich · 2D

Titan Souls
Shared: Souls-like · Pixel Graphics · Boss Rush

Finding Paradise
Shared: Pixel Graphics · Story Rich · 2D

OMORI
Shared: Pixel Graphics · Story Rich · Psychological Horror

Hollow Knight
Shared: Souls-like · 2D · Story Rich

Rubinite
Shared: Pixel Graphics · Boss Rush · Souls-like

Until Then
Shared: Pixel Graphics · Story Rich · Emotional

SANABI
Shared: Pixel Graphics · Story Rich · 2D

BOKURA
Shared: Pixel Graphics · Psychological Horror · 2D

Blasphemous
Shared: Souls-like · Pixel Graphics · 2D

OneShot
Shared: Pixel Graphics · Story Rich · 2D

Urban Myth Dissolution Center
Shared: Pixel Graphics · Psychological Horror · 2D

Nine Sols
Shared: Souls-like · 2D · Story Rich

To the Moon
Shared: Story Rich · Pixel Graphics · Emotional

Dead Cells
Shared: Pixel Graphics · Souls-like · 2D

Black Myth: Wukong
Shared: Souls-like · Story Rich · Action

Hollow Knight: Silksong
Shared: Souls-like · 2D · Story Rich

DISTRAINT: Deluxe Edition
Shared: Pixel Graphics · Psychological Horror · 2D

Undertale
Shared: Pixel Graphics · Story Rich · 2D

STAR WARS Jedi: Survivor™
Shared: Souls-like · Story Rich · Action

Blasphemous 2
Shared: Souls-like · Pixel Graphics · 2D

Just a To the Moon Series Beach Episode
Shared: Story Rich · Pixel Graphics · Emotional

Sally Face - Episode One
Shared: Story Rich · Psychological Horror · Mystery