Kiril Jajaev serves as the general director of the Anti-Thanatos Plan, known as the D-Project. In terms of appearance, he is characterized by white hair and a prominent scar on his forehead. His personality is notably informal and indiscreet, as he is described as having a loose mouth and frequently making inappropriate remarks without regard for the situation.

Within the story, Kiril holds a high level of authority over the operations aimed at countering the Thanatos threat. Following the Spirytus incident, in which civilians witnessed dragons, he made the decision to publicly announce the existence of Thanatos and the Dragonaut squad. However, despite this disclosure, he chose not to reveal the truth behind the shuttle accident, a detail that was no longer necessary to keep hidden; this omission may have been an act of retaliation against Jin due to his uncooperative behavior with the ISDA. Regarding his broader motivations, he has made statements that suggest a desire to initiate war against Thanatos.

Regarding his development throughout the series, specific details about his personal growth or changes in his worldview are not available. Similarly, there is no information on his notable abilities or any specific combat skills he might possess. Information concerning his key relationships, including detailed interactions with other main characters beyond his professional capacity and his potential animosity towards Jin, is also absent from available records.