It’s…Natsu-Comic

Yūto and Haruka attend the summer Comiket convention together, but since it is the first time for both of them, they underestimate the massive scale and hoards of people who attend. Mika, Hazuki, and Nanami tag along in disguise and help Haruka obtain a dōjinshi she wanted, and to get her out of trouble when people started taking pictures of her.

Synopsis excerpt via Kitsu.