Prism Rain (レインボウシャワー Reinbou Shawā, lit. "Rainbow Shower") is a technique exclusive to Aqua that debuted in Kingdom Hearts Birth by Sleep. The attack consists of firing a salvo of rainbow-colored orbs at the targets.
Mechanics
In Kingdom Hearts Birth by Sleep, Prism Rain is a Shotlock that has a maximum level of 5 and max lock of 16. After the initial volley, the user can perform extra attacks by pressing 
in a timely manner to fire additional projectiles, based on the user's timing rating.
In Kingdom Hearts 0.2 Birth by Sleep -A fragmentary passage-, Prism Rain is a Shotlock that has a max lock of 28. After the initial volley, the user can fire up to three additional salvos by pressing in a timely manner, based on the user's timing rating.
In Kingdom Hearts III, Prism Rain is the default Shotlock of the Master's Defender Keyblade and has a max lock of 28. When activated, Aqua hovers in the air and fires a burst of light projectiles at the enemy, with the amount of projectiles depending on the number of locks. If 28 locks are achieved, the user can fire up to three additional salvos by pressing in a timely manner, with the amount of projectiles depending on the user's timing rating. A "TOO SLOW" or "TOO FAST" rating will result in 3 projectiles being fired, a "GOOD" rating will result in 14 projectiles being fired, and an "EXCELLENT" rating will result in 21 projectiles being fired.
Learning Prism Rain
Kingdom Hearts Birth by Sleep
- Aqua obtains Prism Rain from a chest in the Ship Hub.
Kingdom Hearts 0.2 Birth by Sleep -A fragmentary passage-
- Aqua unlocks Prism Rain after releasing the Gear on the floating path in Castle Town.
Kingdom Hearts III
- Master's Defender has Prism Rain as its Shotlock.
Etymology
A prism is a small glass that is used to refract light into its seven component colors. The component colors of light match the colors of the projectiles launched during the execution of Prism Rain.