A native alter and close friend of Kimishima. Her alter ability is "Noble Tempest." When it is active, anything her hair touches turns into water and a small octopus alter takes the appearance of a hair ornament. She does not like to fight, but uses her power when she needs to. Later on, she gets captured and, under threat of HOLY withholding medical treatment from her brother, has her alter abilities refined extensively. This allows her to completely control water, cause chemical reactions with the elements in the water and manifest a gargantuan alter by using a special conchlike apparatus hanging from a necklace. While battling Kazuma, she finds out her brother has died, and dies herself soon after, completely losing the will to live. In the manga, she marries Kimishima and they have a child together. In the anime, Ayase seemed to have taken a liking towards Kazuma, though it is not confirmed if she had the same feeling for Kimishima.
Noble Tempest (Pre-Refinement): Before the experimentation, Ayase's "Noble Tempest" manifested in the form of altering her hair to a deep teal color and combining millions of individual hair follicles into singular large strands, which appeared to "flow" in all directions, almost akin to seaweed in the water. A pair of miniature conch shells with pinkish-red orbs were attached to Ayase's hair on either side.
- Liquefaction: With her "Alter" active, Ayase's hair strands are capable extending for up to several meters from Ayase herself, which can then liquefy any solid substance that comes into physical contact with her hair into puddles of water within seconds. While shown to easily transmute synthetic materials such as glass and metal, it is unknown whether Ayase's liquefaction is effective on organic tissue. The entire process is completely silent, making it an ideal "Alter" power for covert operations or espionage. Ayase appears to have to enter a state of deep focus in order to direct her hair strands in a certain direction.
Noble Tempest (Post-Refinement): After the experimentation, Ayase's "Noble Tempest" has an additional feature to her modified hair; in the form of a tall humanoid figure, with sea-blue skin, vaguely reptilian features, elongated fingers and nails. It also seems to have a trio of purple tentacles portruding out of each shoulders, as well as a mask-like face. Stress to the improved "Noble Tempest" from overusage manifests as cracks upon the humanoid "familiar". Ayase also has a peculiar necklace produced on her neck.
- Wave Generation: Post-refinement Ayase has obtained a far more general manipulation of water from the experiments, resulting in the ability to apparating a large and violent volume of water from her feet, flowing in all directions. Capable of smashing apart building-sized boulders with sufficiently large quantities.
- Whirlpool Twister: Post-refinement Ayase can also freely manipulate the flow and velocity of currents within a body of water, resulting in the formation of large whirlpools underwater (or twisters above the surface), which viciously rotate victim(s) until they are rendered unconscious or are severely damaged from the momentum of the water. They are often left to drown in the water following their usage.
- Sodium-Magnesium Burst: By manipulating the presence of sodium and magnesium atoms within a body of water, post-refinement Ayase can trigger immediate and multiple explosions in rapid succession. They do not appear to contain a large amount of raw firepower (even base Kazuma was only moderately injured by them): their real danger is the combination of the sheer rate Ayase can trigger the bursts and the fact that they accentuate the danger of drowning underwater.
- Oxygen Bubble: Post-refinement Ayase can also utilize the element of oxygen present in water to produce large bubbles for extended sustenance underwater. While it can be beneficial for continued survival, Ayase has used it primarily as a humiliation tactic to lure in victims, only to continue her assault at leisure.
- Self-Liquefaction: Post-refinement Ayase appears to be able to transport herself and "Noble Tempest" underwater by phasing into the water itself (though this is admittedly conjecture).
- Icicle Rain: By freezing select areas of a body of water to sub-zero temperatures, post-refinement Ayase is capable of producing razor-sharp icicles and launching them like missiles towards a target while submerged.