Nagi Jinno exists as the New Angelic Gaia Interface (N.A.G.I.), an artificial angel forged by Heaven to reduce dependence on vulnerable human or angelic warriors during critical, high-risk scenarios where conventional forces fail or are compromised. Her activation triggers solely under extreme threats, such as Hikari Jinno's abduction by demonic forces or Rika Manabe succumbing to a debilitating spell that removes her from combat.

Manifesting physically as a blue-haired virtual girl, she materializes unexpectedly within Naoto Jinno's bath at a critical moment, revealing her nature as a non-human combat program. Her core mission targets rescuing Hikari and neutralizing potent new enemies, including an advanced robotic devil and the resurgent antagonist Misty May. Her digital composition grants her the ability to regenerate from damage, enabling riskier engagements than organic angels can undertake. A critical operational protocol necessitates Naoto engage in sexual acts to generate the "Amore" energy required for her transformation into the combat form "Angel Zero" or "Jibril Zero".

Her deployment signifies Heaven's strategic pivot in the ongoing conflict, prioritizing operational efficiency and minimizing casualties through the use of artificial beings instead of living warriors.