I might as well write a review for this as the vast majority of people don't seem to be able to understand what this short is trying to do. In my humble opinion, this is a masterpiece as it perfectly encapsulates the feelings of my experience watching Monogatari. TL;DR at the bottom. Story - 10 Since this is less than 4 minutes long, it's obvious that they have to be economical with there time. Therefore the story is simple: it's just Araragi reminiscing about the five main girls of the series and that's all it needs to be. Some may claim that there should have been 'more' somehowbut, i think you're judging it by the wrong standards.

I think it's best to judge it like a piece of music, with the dialogue being the lyrics. The best stories and, by extension, music conveys the emotions that the writer was feeling while writing - lets you experience those emotions. Koyomi History does exactly that. It puts me in the frame of mind to reminisce on the time I've spent watching these characters struggle, grow, laugh, love and hate. With very few words it conveys the accumulative emotion of the entire series for me.

Art - 10
Now, sure, there's very little animation and no backgrounds but, does there need to be? I think not. By keeping the visuals minimal - a vast departure from the usual style - it allows you to concentrate fully on the characters, assisting that reminiscence. Araragi not even being shown in the short also helps keep this focus - it's not about his experience.

Sound - 10
Again, just because the only sound is the voice acting doesn't mean that it's bad. I'm probably getting repetitive but, it's all in service of creating the best atmosphere to reflect there's nothing but the characters.

Character - 10
It's Monogatari, so yes the characters are great and they all get to show what makes them great. This stimulates that contemplative mood. Some may argue that it doesn't offer anything 'new' and to that, I'd say it's called Koyomi HISTORY for a reason.

Enjoyment - 10
As you can probably tell, I enjoyed it. It allowed me to experience some of my fondest memories again and somehow gave me lots to think about despite hardly saying anything at all.

Overall - 10
This is a masterpiece as it delivers the emotional impact of an entire series in less than four minutes. However, this is only for people who love Monogatari and it's characters.