Oldest mention to Demon Core as local favorite I could find was timestamped 2016/12/05 23:51, but they don't keep formal logs and they really don't like things "brought outside", so I'm not going to link it.

Maybe there could be mht files in someone's basement somewhere, but I have no data to present at this instant, mostly just oral history. Sorry for that.

edit: oldest post tagged Demon Core on Pixiv dates back to 2016/01/17, so kym is verifiably off by years.

edit: there's a KanColle themed image post in Nico nico seiga dated 2017/06/18 featuring a "borrowed" Demon Core-chan 3D model, which meams the design existeed for some time.

edit: this blog post dated 2014/09/30 links to a deleted Touhou video with Demon Core in title: https://1ni.co/2014/09/30/project20140930_6/

I always figured that it was originally a Touhou meme because the right foot of the final boss, Utsuho Reiuji, from Touhou 11 (2008) is based on the Elephant's Foot from Chernobyl.

follow-up: a comment[0] in TFA claims 2011/04/03 article on Gigazine.net to be the origin, however that itself links to 2011/03/29 slashdot.jp diary entry[2] which is apparently written by translator for ja.wikipedia article[3] created at 2011/03/28[1]. These are also pre-memeization, but just articles for curiosity. There must be some point between 2011 and 2014 that it became a meme.

0: https://doomsdaymachines.net/p/the-meme-ification-of-the-dem...

1: hey, it's not nice thing to say, and I understand that writing for the Gigazine is not an easy job, but frankly,

2: https://web.archive.org/web/20110404124748/http://slashdot.j...

3: https://ja.wikipedia.org/w/index.php?title=%E3%83%87%E3%83%B...