Daitetsu Kunikida holds the position of Chief Director at the Terrestrial Administration Center (TAC), a covert government entity dedicated to countering Aragami threats. He adopted and raised Kaede Fujimiya, twin sister to Momiji Fujimiya, as his own daughter. During her upbringing, he harnessed Kaede's distinctive abilities to trace and eradicate Aragami, strategically employing her as a critical asset to advance TAC's operational goals. This methodology involved leveraging her powers for the organization's benefit.

Kaede's ultimate sacrifice inflicted deep guilt and sorrow upon Kunikida, fundamentally altering his conduct toward the surviving twin, Momiji. Resolved against repeating past errors, he deliberately refrained from exploiting Momiji's comparable abilities. Instead, he focused on treating her as an ordinary girl under TAC's guardianship, manifesting a more nurturing and paternal leadership approach.

Within TAC, Kunikida operates in a professional leadership capacity, frequently coordinating field missions from agency headquarters and occasionally piloting a Citroën XM during operations. His professional interactions include Ryoko Takeuchi, a former police officer, with whom he shares an unspoken mutual romantic interest. His management duties extend to overseeing a varied team comprising scientists like Azusa Matsudaira and field agents such as Koume Sawaguchi and Yoshiki Yaegashi.