Sometimes when you defeat an enemy, a bonus effect will occur. This is called a PSE (Photon Sensitive Effect). The effects can vary from boosting the character's abilities, to increasing EXP, or other effects. A PSE chance occurs when a PSE is about to activate. Changes in weather also affect the occurrence of a PSE.
When activated, a PSE occurs around the player, with an icon displayed in the upper right corner of the screen. A system message is also displayed to explain the impact of the PSE. Continuously defeating enemies while a PSE is activated will level up that PSE and strengthen its effects.
When a PSE reaches its maximum level, a PSE Burst occurs. The effects of a PSE are enhanced during a burst, also increasing the drop rate of rare items and more enemies spawning. A PSE Burst time limit is displayed on-screen while the burst is activated, and can sometimes be extended by defeating enemies.