Future Diary

Oh! Mirai Nikki Redial was expected by me, since at the end of the manga shows him in a totally different place, and in the anime at the end after the credits shows Yuno appearing and Yuki looked at her in awe, the first episode of Mirai Nikki Redial only shows how she got in there. Sorry for the bad english.  

are like extra episodes with murumuru that pass after the ending:

http://www.youtube.com/watch?v=0GPPGQMALGYhttp://www.youtube.com/watch?v=0hzxfib87eM

  zerochan

at first I also did not understand

as you've seen throughout anime, know that the first world yuno turned god and thought he could relive yuki but failed,so she returned in the past (back when in the past it creates another world), and killed the second world yuno and lived the game again with yuki 2 world with the help of the world murmuru 1.When the game's second world  was ending she returned again in the past to kill the 3rd world yuno but yuki stop her.In the scene that the yuno 2 world dies she realizes that was not unhappy her parents loved her, but her mother had psychological problems.

So in the second world yuno dies and yuki turns god in 2 world along with the 2 murumuru world too, but Yuki is alone and unhappy. During the third world do not have the game because the Deus ex machina does not die and the  yuno of 3rd world feel something missing .If you saw the end of the little letters after, yuno can meet the second world yuki.