Games like Daisen
Games like Daisen include ULTRAKILL, Bright Memory, Bright Memory: Infinite, DUSK, and MULLET MADJACK. We matched them by the tags players give Daisen on Steam (Fast-Paced, Female Protagonist, Arena Shooter, FPS, and Boomer Shooter): closest matches first, and among equally close ones the better-known games.

ULTRAKILL
Shared: Fast-Paced · FPS · Boomer Shooter

Bright Memory
Shared: Female Protagonist · FPS · Hack and Slash

Bright Memory: Infinite
Shared: Female Protagonist · FPS · Shooter

DUSK
Shared: FPS · Fast-Paced · Boomer Shooter

MULLET MADJACK
Shared: Fast-Paced · FPS · Boomer Shooter

Guns and Nuns: Storming Hell
Shared: Fast-Paced · Female Protagonist · FPS

BRAZILIAN DRUG DEALER 3: I OPENED A PORTAL TO HELL IN THE FAVELA TRYING TO REVIVE MIT AIA I NEED TO CLOSE IT
Shared: Arena Shooter · FPS · Boomer Shooter

DOOM Eternal
Shared: FPS · Fast-Paced · Shooter

Devil Daggers
Shared: Fast-Paced · FPS · Arena Shooter

Half-Life: Alyx
Shared: FPS · Female Protagonist · Shooter

DOOM
Shared: FPS · Fast-Paced · Shooter

Selaco
Shared: Female Protagonist · FPS · Boomer Shooter

Turbo Overkill
Shared: FPS · Boomer Shooter · Fast-Paced

Ion Fury
Shared: Fast-Paced · FPS · Boomer Shooter

Beyond Citadel
Shared: Female Protagonist · FPS · Boomer Shooter

Neon White
Shared: Fast-Paced · FPS · Shooter

AMID EVIL
Shared: FPS · Boomer Shooter · Arena Shooter

ICEY
Shared: Female Protagonist · Hack and Slash · Anime

Prodeus
Shared: FPS · Boomer Shooter · Fast-Paced

Half-Life 2
Shared: FPS · Shooter · Sci-fi

VOID/BREAKER
Shared: FPS · Bullet Hell · Fast-Paced

I Am Your Beast
Shared: Fast-Paced · FPS · Boomer Shooter

HYPER DEMON
Shared: Fast-Paced · FPS · Arena Shooter

Trepang2
Shared: FPS · Shooter · Fast-Paced