Astharoshe "Asthe" Aslan, Duchess of Odessa and Kiev, serves as an undercover agent for the New Human Empire. Known for her straightforward demeanor and disdain for Terrans, she views them as barbaric and unintelligent, influenced heavily by Empire propaganda and her limited interactions with humans. Asthe finds the term "vampire" offensive, preferring to identify herself solely as a Methuselah. She wields the Sword of Gae Bolg, a formidable Lost Technology weapon that generates a plasma blade from ionized xenon gas, capable of slicing through anything.
Her perspective on humans begins to shift when tasked with arresting Endre Kourza, a vampire mass murderer whose actions threaten to ignite a war. Partnered with Father Abel Nightroad from the AX Agency, their mission takes a personal turn when Endre kills Asthe's partner. Consumed by rage, Asthe inadvertently destroys the Rialto Bridge, causing numerous human casualties. Abel suffers injuries protecting her from her own weapon during the chaos. Deeply remorseful, she learns to control her emotions better during their second confrontation with Endre, leading to his arrest. Initially dismissive of Abel's claim to partnership, Asthe eventually respects him enough to acknowledge him as such, also becoming more accepting of humans.
Their collaboration becomes pivotal in secret peace negotiations between the Vatican and the Empire. Asthe later shelters Vatican diplomats and the Earl of Memphis following an assassination attempt on Cardinal Caterina by the Rosenkreuz Orden. This event positions her as a key figure in thwarting further attempts by the Orden to instigate conflict between Methuselah and Terrans.
In the novels, Endre murdered Countess Len Yearnoshe, whereas in the anime, her deceased partner is male, implying a romantic relationship. In the animated series, Asthe is first assigned to investigate a suspected vampire-related incident, reluctantly partnering with Abel. Though often stern, Asthe demonstrates caring and understanding traits occasionally. A proficient fighter, she uses a versatile spear that extends on command and releases powerful energy blasts.
