Yuno Gasai is the love interest of Yukiteru Amano in the manga/anime series Mirai Nikki. She's the Second diary user. Smart, beautiful, and diligent, to most students she is seen as the model student but in reality, she is secretly obsessed with Yuki when he unknowningly gives her a sole reason to live for, and constantly stalks him. She is so obsessed with Yuki that she is willing to hurt or kill anyone who hurts him and is constantly jealous if anyone other than her is getting close with Yuki. So obsessive was her love that she won't hesitate to sacrifice them because to her, the only important thing is that she and Yuki survive the game. Her obsession and possessiveness of Yuki is so extreme that she has no concern for anyone else's well-being: she frequently states to Yuki that he should not care about what happens to his friends. Her diary is the Yukiteru Diary, a stalker diary which gives her details of whatever Yuki is doing in the present 10 minutes. Because it only focuses on Yuki, her diary does not specify anything about her unless it has to do with Yuki. But by working together with Yuki's Random Diary, they are able to solve their diaries' weaknesses.
She's eventually revealed to come from the 1st world, the original timeline in which where she was the victor of the game, and was driven mad when she resurrected Yuki but not his soul. This prompted her to travel to 2nd world, where the current story took place as she murdered the 2nd world Yuno and took her place. When Yukiteru finds out the truth, she tries to kill him so that she can become god and go back in time once again. In the end, though, Yuno can't bring herself to do it and kills herself so that Yukiteru becomes god instead. However, her memories are transferred to 3rd world Yuno and she becomes the god of her own world to be with Yukiteru.