|“||Life used oxygen because of the energy it contained. Likewise, my soul wishes for strength. I need hatred and bloodlust. Without them, I can't fight back against the cold world||”|
–Kotarou's words as he Rewrites his aurora until it evolves into beasts
Aurora Beasts are merciless blades made of aurora used by Kotarou that brutally murders anyone and anything that tries to harm him.
The blades are made of Kotarou's aurora which is multi-colored, but has a furoucious personality. When they first emerge from the slits in Kotarou's wrists. They resemble the jaws of a beast.
Akane's Route: When Kotarou is being hunted down by five hound-familiars in the forest, he is forced to Rewrite his body and his aurora in order to fend them off. While rewriting, he mentally asks for 'strength' and 'bloodlust' while using his feelings for Akane as fuel to gain the power to protect her. This rewriting causes Kotarou's aurora to spawn a personality based on his murderous instincts (Similiar to Kagari's Miracle Ribbons being the manifestation of her defensive instincts). Its form is the most commonly used form in the route.
- The blades are sharp enough to pierce through most enemies skin with the exceptions being, Takasago and the Earth Dragon.
- Usually Kotarou loses aurora when he uses it but his Aurora Beasts retreat into his body after being used.
- Like the Key's ribbons, they automatically defend Kotarou from any close-range attack or projectile.
- They can respond to an enemy faster than Kotarou can, as seen in Gaia's tunnels when they killed Guardian's hunters the moment they tried to harm Kotarou.
- Kotarou only uses this ability in Akane's Route.