Izuko Gaen is highly intelligent and deeply informed about the supernatural world, often surprising others with the extent of her insight. Despite her youthful appearance, she possesses an encyclopedic understanding of oddities, folklore, and even the personal histories of individuals like Koyomi Araragi and Tsubasa Hanekawa. She frequently emphasizes her intelligence through her trademark catchphrase: “There is nothing that I don’t know. I know everything,” a direct counterpoint to Tsubasa’s own mantra.

While the absolute truth of her claim is uncertain, Gaen has a sharp ability to exploit gaps in others’ knowledge. She skillfully uses what she knows and what others don’t to manipulate conversations and undermine others’ confidence. A notable example is how she challenges Tsubasa’s belief in her own intellectual superiority, subtly shifting the balance of control in their interactions.

Izuko Gaen is portrayed as a middle-aged woman with long, wavy brown hair and striking orange eyes. Her fashion sense reflects a hip-hop influence, characterized by a vibrant and casual style. She typically wears a loose light green shirt layered over a black sweatshirt, paired with maroon baggy pants and running shoes. Her accessories include a white baseball cap with a light green rim, a smiley-faced necklace, and orange headphones that rest around her neck.

A notable visual motif associated with Gaen is the recurring swirl of rainbow-colored clouds that appear in the background whenever she is present, adding an enigmatic and otherworldly flair to her appearances.

During her college years, Izuko Gaen served as the upperclassman to Meme Oshino, Yozuru Kagenui, and Deishuu Kaiki. Together, they were members of the Occult Research Club, where Gaen played a leading role in their studies of supernatural phenomena. Although she appears to maintain a general familiarity with her former juniors, she has shown a particular dislike toward Yozuru Kagenui for reasons that remain unclear.

Gaen was also involved in the creation of Yotsugi Ononoki, an artificial being constructed through forbidden means. As a consequence of her participation, she was afflicted with a supernatural curse one that compels her to “know everything,” aligning with her infamous catchphrase.

Additionally, Gaen claims familial ties to Suruga Kanbaru, identifying herself as Suruga’s aunt and the sister of Tooe Gaen.

Meme Oshino
Gaen was Oshino’s senior during their time in the Occult Research Club in college. While the two share a long history, Gaen often references him with a mix of respect and irritation, especially due to his tendency to abandon situations he finds troublesome.

Yozuru Kagenui
Although they were once fellow club members, Gaen has expressed visible dislike toward Yozuru. Despite working within the same field of oddities, their methods and ideals often appear to conflict.

Deishuu Kaiki
Another of Gaen’s juniors from the Occult Research Club, Kaiki shares a similarly complex relationship with her. Gaen tends to refer to him in a matter-of-fact tone, aware of his manipulative nature but not overly antagonistic.

Yotsugi Ononoki
Gaen played a role in Ononoki’s creation, contributing to the process that turned her into a tsukumogami. Though she does not act as Ononoki’s handler, Gaen treats her as both a product of her past actions and a reminder of the consequences she bears.

Suruga Kanbaru
Gaen claims to be Suruga’s aunt, stating that she is the younger sister of Tooe Gaen, Suruga’s mother. She occasionally provides cryptic advice and assistance to Suruga, though her motives are often layered and not immediately clear.