Story: 6/10 Art: 5/10 Sound: - /10 Characters: 10/10 Enjoyment: 7/10 Koyomi History is an animated adptation of the homonym side story published in the Madogatari Exhibition pamphlet, written by Nishio Ishin (Also known as NISIOISIN), the Monogatari Series author, and it talks about Koyomi Araragi remembering the girls he tried to help. This special "episode" is represented on a white background, it has no sounds (except for the characters voices)(this is why i have not rated the sound) and we can see all the main Bakemonogatari characters, with Koyomi as protagonist. Also Koyomi History is placed (by the reading order) after Orokamonogatari, in the Off Season of the novel that doesn'thave an anime adaptation yet.
I think this episode doesn't deserve a 7 as overall rating, but I personally enjoyed to watch this side story animated (I'm a huge Monogatari Series fan, that's why) even if the art is not this good (really minimal and doesn't literally add anything very important to the episode) and there is no background sounds.