Sauce please
http://www.pixiv.net/member_illust.php?mode=medium&illust_id=59980632
looks like it's a one-off image. artist has a couple of doujins with mika and rika though.
https://nhentai.net/search/?q=%E8%8C%B6%E8%8F%93%E5%B1%B1
>>15271084
thank you anon