TV-Series
Description
Gekko Nanase is the younger brother of Takeshi Nanase, born approximately one year later. He has neck-length dark purple hair featuring one distinctive long strand on the right side and red eyes, standing at average height. While initially calm and reserved, his demeanor gradually shifts to appear more sociable and upbeat, especially around Takeshi and Kurumi Isoshima. This exterior conceals a deeply possessive and obsessive attraction toward Kurumi, fueling intense jealousy and hatred for his brother. His fixation manifests in remorseless violence against others, including family, indicating a lack of regard for human life.

In early life, Gekko practiced kendo with Takeshi, demonstrating superior skill, and developed feelings for Kurumi during childhood. During middle school, when he learned of Kurumi and Takeshi's fake relationship—which he misinterpreted as Takeshi exploiting Kurumi's vulnerability after a traumatic stalker incident—their conflict escalated. A physical fight resulted in Takeshi accidentally pushing Gekko into the path of a car, permanently injuring Gekko's left leg and ending his kendo pursuits. Gekko falsely attributes malicious intent to this act, cementing his hatred. He later discovers their mother, Youko Nanase, orchestrated the assassination attempt to prevent him from becoming like the antagonist Kazuma Ryuusenji, leading Gekko to retaliate by assaulting her.

Gekko's involvement intensifies after training under Kippei Washizu and joining the antagonistic Ghost Trailers to gain magical abilities to combat Takeshi. His acceleration magic, Angel Hunt, enables teleportation and high-speed movement, including the near-invisibility spell Accelerate. He wields the Angel Blade and later modifies Takeshi's stolen Aspect weapon, Twilight, into Bloody Twilight—a version that chains and controls Twilight's human form. Additional spells include Protection for defense and Float for aerial mobility.

Upon transferring to Subaru Magic Academy, Gekko feigns reconciliation with Takeshi to lower his guard. He participates in the Ghost Trailers' assault on the academy, defeating Takeshi in battle and abducting Kurumi. In their final confrontation, he stabs Kurumi as she shields Takeshi, triggering Takeshi's resolve to kill him. Their battle culminates in a temporal displacement to the past, orchestrated by Academy director Momoka Shijou, leaving their conflict unresolved. Gekko's actions throughout are fueled by an inferiority-superiority complex and desire to usurp Takeshi's life, including claiming Kurumi and Twilight.

Gekko's relationships are defined by antagonism: his hatred for Takeshi forms a Cain-and-Abel dynamic, his obsession with Kurumi borders on pathological, and his betrayal of Youko underscores his vengeful nature. Ghost Trailer allies find his behavior off-putting, reinforcing his isolation. His legacy intertwines with Kazuma Ryuusenji; Youko's failed assassination aimed to prevent Gekko's transformation into this figure, though implications linger that Gekko may still embody this destructive potential.