Gaen, Izuko

She is a young-looking woman who wears hip-hop-style clothes that are too big for her. She is the most knowledgeable specialist in the series. Gaen claims to know everything, to the degree where she can predict the future; as a result, she likes to brag about this and her catchphrase is "There is nothing I don't know, I know everything." Although the credibility of her claims over "knowing everything" may be debatable, it can be argued that she is good in taking advantage of what she knows and what other people do not know, allowing her to break down a person's confidence, like Tsubasa's confidence in her knowledge, for example.

She has five cellphones and gave Koyomi three of her contact numbers during the events of "Shinobu Time." Compared to Meme, who wants compensation, Kaiki, who works for money, and Yozuru, who works for free, Gaen demands "friendship" as a form of payment. In other words, she demands that people owes her a favors and doesn't pay her now, but later. She doesn't tell when or what favors she wants done and that she is essentially building a network of people who owe her favors, and use these favors as transactions to get what she wanted done.

She was the upperclassman of Oshino, Kaiki and Yozuru but has shown some form of dislike towards Yozuru for some reason and it is implied that she has a connection to Kanbaru as her last name is the same as Kanbaru's mother.

In Koyomi's case, in exchange for helping him during the events in Onimonogatari, Gaen demanded Koyomi to introduce her to Kanbaru but to keep a secret that Gaen is Kanbaru's aunt.