As costume (cosplay) events go for anime, this is the big one and it was the 90th time the Comiket show has been held. The massive 3 day event was held at the Tokyo Big Site convention center and brought together fans from all generations of anime.
When I first came to Japan in the early 90s, I was brought to the event by my friend and I'd never seen such a thing. The costumes are simply amazing but it was also inspiring to see all the independent comic designers and producers and I remember buying some of their self printed books (wish I kept them). Here is a vendor selling some anime.
If you ever come to Japan and want to see cosplayers then you can see them in Harajuku but if you are really into the big anime events is where it is at. If you are into cosplay, in general, then Halloween in Shibuya is where it is at. It has almost become a week long event now of people dressing up walking around Shibuya posing for pictures and videos.
Here is a video showing the Halloween fun times
Below are some links to articles about the Comiket 90 show
Rocket 24 news story with lots of pics: http://en.rocketnews24.com/2016/08/15/the-swimsuit-idol-and-swimsuit-idol-cosplayers-of-summer-comiket-2016%E3%80%90photos%E3%80%91/
Gorgeous girls in costume: http://www.animatetimes.com/news/details.php?id=1471243970
Blog with social media posts with lots of pics of the event and costumes: http://yaraon-blog.com/archives/90020
If you ever do come to the event, please realize these young people take it very seriously and are just using costumes to express themselves possibly in ways they can't do in the normal rigid life in Japan. Some are of the costumes are sexy but they staying true to the characters they are portraying. So if you ever come here and want to take a photo. Just ask politely and don't be creepy. :)