Eisen is one of the Eight Guardians, the Genbu of Heaven, and a half-brother to the Emperor who renounced his imperial status to become a monk. He carries himself with refined grace and a gentle demeanor, consistently avoiding conflict and displaying a strong aversion to violence. His elemental affinity is Water, and his dragon jewel rests in the palm of his left hand. A skilled flutist, his music reflects his calm and artistic spirit.

His choice to leave the Imperial Family underscores a deep desire for peace and introspection, aligning with his compassionate nature and his role as a spiritual protector among the Guardians. Eisen’s abilities focus on purification and support, harmonizing with both his Water attribute and monastic life.

He emerges as the seventh Guardian during a critical encounter involving a cursed eight-stringed koto that casts Akane into a sleeping curse. Eisen’s intervention proves pivotal in breaking the curse, demonstrating his unique value to the group through specialized knowledge and skill.

Throughout his journey, Eisen grapples with the tension between his pacifist ideals and the necessity of conflict to protect others. This inner struggle forms a central part of his development, as he learns to adapt his non-violent principles to the duties of a Guardian. Despite his gentle disposition, he does not hesitate to engage in battle when the Priestess or the realm is threatened.

Across all portrayals, Eisen remains a figure of kindness, introspection, and musical talent. His contributions emphasize support and healing, bolstering the group through spiritual strength and empathy.