Kagero Donne, a seasoned operative of the Other Suppression Force with 12 years of service, wields psionic invisibility—a skill that secured his recruitment as an adult. His origins trace back two millennia to Shin Daniel, a lunar colonist dispatched to undermine Earth’s recovery efforts. When the Extinction Barrier isolated the planet, he was marooned, forced to shed his identity for the alias "Kagero Donne." His artificial crimson eye and sun-bleached hair remain stark echoes of a life he conceals.

Once a priest and assassin serving Togetsu, Kagero abandoned his mission to assassinate Chairman Joe Sumeragi after uncovering the organization’s manipulation of Red Strings. Buried beneath his charismatic, jesting exterior lies grief over his family’s lunar demise and the loss of his left eye during the Spring of Extinction—wounds he avoids confronting, even as camaraderie with allies like Kasane Randall, Yuito Sumeragi, and former trainee Tsugumi Nazar slowly rekindles his fractured purpose. His candid discussions with Kasane about the weight of lives taken reveal a conscience grappling with violence’s moral toll.

In battle, Kagero’s stealth expertise shines: vanishing to deliver lethal strikes, exploiting abilities like Backstab and Assault Vision. Enhanced SAS protocols grant prolonged invisibility post-attack, auto-activation when wounded, and synchronized Crush Vision assaults, cementing his role as a tactical linchpin against Others.

Ultimately, Kagero channels his lingering guilt into the Lunar Surface Survey, joining Kasane’s mission to bridge Earth and moon. Though initially reluctant, Tsugumi’s urging propels him toward atonement—a step from haunted past to a future forged in hope, where reconciliation, not sabotage, defines his legacy.