Hijiri Kasuga

16 years old, height: 156 cm, measurements: B 83/W 56/H 84. A member of the Gospel Exploration Society (Ish-Kariote). She awakened as a mage from a young age and was dispatched under the orders of Master Liber to monitor Arata and eliminate him if necessary. She was a former mage of the Royal Liber Academy. Her specialized magic is the same as Arin's, the Holy Ritual Magic (Chaotic Rune). Her "Library" and "Holy Ark" are Wrath (Ira), and her "Themes" are Ruin (Ruina), Creation (Partum), and Disassembly (Analysis). She is also the original holder of the "Astil Manuscript" and the "Ilias Fragment."

Due to her parents' death in an accident, she was taken care of by Arata's family, but in reality, it was Arata's parents who died in the accident. To prevent Arata from awakening as a Demon Lord prematurely due to the shock of the accident, a suggestion was placed, and they lived together under the belief that they had taken in a cousin whose parents died in an accident. She is a blood-related cousin, born to Arata's paternal uncle, an agent of the Liber Academy, and his wife, who also belonged to the Liber Academy. She is caring but can be quite nagging. Just before being sent to the "World of Nothingness" by the "Collapse Phenomenon," she handed the legendary magic book "Astil Manuscript" to Arata.

The current Hijiri is not the Hijiri known to Arata, but an embodiment of a powerful anti-Demon Lord weapon harboring the Demon Lord Factor, aiming to destroy the world. However, it is revealed that her actions were driven by a desire to save Arata, a Demon Lord candidate, from the system of destruction and rebirth, which she observed countless times in the world between worlds after meeting the Trinity Seven. She possesses emotions beyond "Wrath" but lacks the concept of "Wrath," and is said to be capable of leading the world to ruin and killing the Demon Lord out of love, a quality referred to by Liber as the potential of the "Usurper King (Surtur)." She endured countless ages by borrowing magic from Lieselotte, repeatedly facing a hopeless loop where everything but herself perished with the revival of the "Goddess of Deep Darkness."

By utilizing the Demon Lord Factor, she has mastered the three themes of "Ruin," "Creation," and "Disassembly," reaching the Trinity. Failing to trap Arata in a different dimension, she donned the manifestation attire of "Wrath," "Seitan," to confront the Trinity Seven but was defeated by Arata and Lilith's "Meteor Dragner," forcing her into temporary rest.

Hijiri has harbored feelings for Arata since long ago, dreaming of becoming "Arata's bride" if not for his power as a Demon Lord candidate. Like Arin, she is one half of the reincarnation of the former "World Tree Priestess" Celestia and possesses the qualifications of the Trinity Seven and the ability as the "Final Activation Key." This was intended so that either could become the Demon Lord's partner, but this similarity became a hindrance when Arata and Arin were trapped in the Nostalgia Library.

In the new chapter of the main story, she is reborn as the embodiment of the Heavenly Emperor's Ultimate Law "Black Emperor Flame Realm," using the Evil God Key collected by Lugh and her own soul as a sacrifice, severing her link with Arin as the "World Tree Priestess." Simultaneously, she acquired the attribute of "Heaven" and the ability to connect to the "Holy Ark," clashing head-on with the intent to kill Arata and free him from the curse of being a Demon Lord. Upon accepting defeat in a one-on-one battle, she became a silent sword, embodying her memories and emotions as infinite black flames in the form of the "World of Destruction," finally returning to Arata. Later, when Arata connected to the world of the Black Emperor Flame Realm, she spoke to his spirit, continuously burned by the black flames, in a manner closely aligned with her original personality, Celestia.