Or, when properly titled: Eun Debate — Genderless, Male, or Female?
Now, some will say female.
Some say male.
Some say genderless.
Headcanons are your own: do not let this change your personal headcanon. However, do keep these facts in mind.
Before I start; let me say that this is researched with knowledge in Japanese and Chinese mythology, and general demonology. I’m not a degree-carrying expert; but I have enough expertise to know what I’m talking about.
Demons, which Eun most certainly is (go ahead: call Eun a spirit — Eun is a demon, why else would exorcists put Eun inside the hairpin, except to seal away Eun’s powers?), are all genderless in mythology. However, because the concept of gender identity (read: what someone feels like and identifies as, gender wise) did not exist in ancient Japan and China, were given genders according to appearance. However, there’s an issue with this: in plenty of myths, the gender seems to switch for the same demon. (See towards the end for an editing note.)
So, which gender is which? The more popularised one? No. It’s safe to say that the demon has no specific gender whatsoever.
What does this have to do with Eun, you ask?
Well, we have to start with Ara, Eun’s host. Ara Haan is based off of a Chinese girl. Her classes don’t help: Little Xia as her base job, Little Hsien, Sakra Devanam, Little Devil, Yama Raja, and the newer ones; Little Spectre and Asura. She’s heavily Chinese influenced. However, Eun is ‘borrowed’ from the famous Japanese myths of the ‘kitsune’ — a nine tailed fox.
The more tails, the more power. The most any kitsune is known to have is nine. Now, there’s something called kitsunesuki — the state of one being possessed by a fox. To explain it briefly:
Kitsunetsuki (狐憑き or 狐付き; also written kitsune-tsuki) literally means the state of being possessed by a fox. The victim is always a young woman, whom the fox enters beneath her fingernails or through her breasts. In some cases, the victims’ facial expressions are said to change in such a way that they resemble those of a fox. Japanese tradition holds that fox possession can cause illiterate victims to temporarily gain the ability to read. Though foxes in folklore can possess a person of their own will, Kitsunetsuki is often attributed to the malign intents of hereditary fox employers, or tsukimono-suji.
Why am I highlighting breasts and own will? If you compare the artwork of all three second classes of Ara; Asura easily has the biggest — and most accentuated — breast form. Unlike Yama Raja’s modern Asian-Western fusion of Chinese and almost European elements in her clothing, and Sakra Devanam’s strictly Chinese elements in her clothing, Asura heads right towards an Asian clashing of minor Chinese elements; but heavy on the Japanese. Why is this? To show, further, how she has accepted Eun of her own free will and released the demon from the hairpin.
Not only that; earliest connections between Japan and China started with the Chinese fox myths:
Japanese fox myths had its origins in Chinese mythology. Chinese folk tales tell of fox spirits called huli jing that may have up to nine tails (Kyūbi no Kitsune in Japanese).
Ara = heavily Chinese.
Eun = heavily Japanese, with obvious Chinese influences.
Eun’s actions towards Ara, and how Ara (as Asura) has accepted Eun, clearly points toward kitsunetsuki. In Japanese myths, often, (editing what I previously said), whilst giving a gender, often just refer to the demon as what they are — a kitsune, and whatever may have you.
tl;dr: Eun is genderless if you sum it all up by reading common Chinese and Japanese folklore and combining the knowledge.
(And just because someone who happen to be a CO of a game does not make them knowledgeable on demons and folklore.)