Someone had a blog about the missing next button on rated m tags. Then Sehun8gfat  replied to the blog with the solution to the missing next button.

"Yeah it's gone for me too. They'll probably fix it later but in the meantime try changing the link like this. 

http://www.asianfanfics.com/browse/tag_rated/sehun/L

this is the link to m rated fics for Sehun and that L at the end is for the latest stories. You can change that easily on the site. for going to the next pages just add /20. since there are 20 fics in one page the second page /20. the third page is /40 and the forth page is /60 and so on.
like this:

http://www.asianfanfics.com/browse/tag_rated/sehun/L/20
http://www.asianfanfics.com/browse/tag_rated/sehun/L/40
http://www.asianfanfics.com/browse/tag_rated/sehun/L/60

I don't know if you knew this or not but if you didn't then this is how you do it XD"

This works on both mobile and on pc. 

I'm so glad she found this temporary solution until the creaters of aff fix this.

Thanks for reading and big thanks again to Sehun8gfat.