Games like Sisters' Aegis
Games like Sisters' Aegis include Vampire Survivors, DJMAX RESPECT V, A Dance of Fire and Ice, Muse Dash, and TouHou Makuka Sai ~ Fantastic Danmaku Festival. We matched them by the tags players give Sisters' Aegis on Steam (Action, Casual, Arcade, Visual Novel, and Bullet Hell): closest matches first, and among equally close ones the better-known games.

Vampire Survivors
Shared: Bullet Hell · 2D · Casual

DJMAX RESPECT V
Shared: Casual · Action · Anime

A Dance of Fire and Ice
Shared: Arcade · 2D · Indie

Muse Dash
Shared: Anime · Casual · 2D

TouHou Makuka Sai ~ Fantastic Danmaku Festival
Shared: Action · Bullet Hell · Casual

Timberman
Shared: Casual · Action · Arcade

Rabi-Ribi
Shared: Bullet Hell · Anime · Female Protagonist

ICEY
Shared: Action · Anime · Female Protagonist

Planes, Bullets and Vodka
Shared: Action · Casual · Arcade

Sixtar Gate: STARTRAIL
Shared: Action · Casual · Arcade

fault - milestone two side:above
Shared: Visual Novel · Anime · Indie

LUFTRAUSERS
Shared: Action · Arcade · Bullet Hell

Gensokyo Night Festival
Shared: Action · Casual · Indie

Touhou Tenkuushou ~ Hidden Star in Four Seasons.
Shared: Bullet Hell · Arcade · Indie

Touhou Danmaku Kagura Phantasia Lost
Shared: Action · Visual Novel · Anime

Vanguard Princess
Shared: Action · Anime · Casual

Mirror 2: Project X
Shared: Visual Novel · Anime · Casual

Exit the Gungeon
Shared: Action · Arcade · Bullet Hell

BALL x PIT
Shared: Action · Arcade · Bullet Hell

Cyberhunt
Shared: Action · Casual · Arcade

TEVI
Shared: Bullet Hell · Anime · 2D

Megabonk
Shared: Action · Bullet Hell · Indie

Bit Blaster XL
Shared: Bullet Hell · Arcade · Action

Windowkill
Shared: Action · Arcade · Bullet Hell