This topic will contain major spoilers. Consider yourself warned. 
It would appear that Mirai Nikki is drawing to a close. Only three of the diary holders are alive and Yuki’s position to be God is almost certain…
…except for the Yuno factor…
So anyone have an idea of who Yuno is? I’ve been wrestling with the idea for a bit now.
I suppose the first question to ask, is if Yuno’s feelings for Yuki are genuine. From all that I can tell, there’s no reason to doubt it. From time to time the story lets us see Yuno’s thoughts, and she’s wholly devoted to him. However she has been known to repeatedly lie and withhold information from Yuki. Of course it’s all in her yandere nature - she’s worried about losing Yuki for herself - but it’s these very secrets that could tear them apart.
The second question to ask, is if Yuno is a real person. We know Yuno isn’t the real Yuno. So when did she replace the real one? Was it years ago or was it when she became a diary holder? This would certainly change the nature of her diary: is it the real Yuno’s entries, or is it the fake Yuno’s entries? Not to mention the promise. Continuing this line of the thought: who created her? Does Muru Muru have a hand in it? I know the most recent chapter revealed, that Muru Muru knows about the 28th entry for Yuno. Quite odd there… Also the whole retinal eye scan deal and the fact Yuno hid it - it seem obvious Yuno is wholly aware of her nature and uses it her advantage.
It does seem so weird that Yuno’s personality, diary, and existence are so perfect for Yuki. She’s the perfect partner for him. The perfect lover for him. The perfect weapon against him. Then there’s two unanswered questions: What does Happy End mean and why is it that only Yuno has that? Obviously we’re lead to believe it means she and Yuki have sex… but that “become one” phrase leaves a lot of room for interpretation. Another unanswered question: exactly what did Deus do to Minene, when he seemed to killed her… but didn’t?
Head hurts…
