Mirai Nikki: Redial

I think both are very similar in the feelings they represent: They are about a strong female character, who is living in a perfect world, but is nonetheless faced with the strange feeling of missing somebody that has never existed: Someone who was integral in creating said world, but who has been forgotten by everyone else. 

*Both series involve the MC having a deep infatuation for the other MC in the story. *Both series have a lead female character that is psychotic and sometimes has no control over what she does. *Both have amazing art work and character design *The two series have Thriller, action, Supernatural, and romance elements *The two are sequels to the original story line