http://doujinshi.mugimugi.org/book/126403/

I've used the information from Doujinshi Database, that lists the circle as Kasakigumi and the artist as Kasaki.
But there're other works at ehentai that lists the circle as Hanasakigumi and the artist as Hanasaki.

Finally, this is missing the last pages. Feel fee to replace if you have the complete version

It is Kasakigumi/Kasaki according to organizer site of COMIC1.

Base +15