Yea, this just started happening to me today too, I don't really know much about this stuff so I don't really know why. It seems to be blocking something from dmm....
Anyways, just whitelist the site and it should go back to working.
Settings -> General -> Scroll down to Exclusions -> URL
Add each of them
https://www.dmm.com/
http://www.dmm.com/
https://cf.r.kamihimeproject.dmmgames.com
http://cf.r.kamihimeproject.dmmgames.com
Click Ok to save and done.
If it still occurs, add the URL that avast keeps blocking and maybe nutaku as well.\
edit: popped up again for me, added more