It's been a couple years since you asked, but the doujin is "このこどこのこかえるのこ" by Carcharias. It was released Dec 12 2010 at C79. Doujinshi.org has more information, and e-hentai has scans (not translated).
It's been a couple years since you asked, but the doujin is "このこどこのこかえるのこ" by Carcharias. It was released Dec 12 2010 at C79. Doujinshi.org has more information, and e-hentai has scans (not translated).