Espers are humans who have awakened supernatural abilities in the world of YiHuan. Their awakening is usually related to anomaly events — when ordinary people come into contact with high concentrations of anomalous energy, there is a very small chance of triggering esper awakening. After awakening, Espers gain combat abilities beyond those of normal humans and are registered with the Bureau of Anomaly Control.
Espers are categorized into six major types based on their ability attributes: Anima, Incantation, Chaos, Psyche, Cosmos, and Lakshana. Each attribute corresponds to different ability characteristics. For example, Anima is inclined toward natural forces and physical enhancement, Incantation specializes in language and talisman-based abilities, and Chaos possesses destructive and reality-distorting properties.
Espers are ranked by power level into S-rank, A-rank, and B-rank. S-rank Espers are the highest tier with the strongest combat abilities and rarest ultimate moves. A-rank Espers are more numerous and form the backbone of the Bureau's forces. B-rank Espers have weaker abilities and typically perform support roles. The Eibon Antique Shop and the Bureau's ETD-4 team in Hethereau gather many powerful Espers.
Espers consume mental energy when using their abilities, and excessive use can cause severe physical strain. Additionally, Espers face the risk of 'loss of control' — when mental energy goes out of control, their abilities rampage, causing serious damage to themselves and their surroundings. Therefore, the Bureau conducts regular checkups and ability assessments for all Espers.