Mirai Nikki - Season 1 Episode 23

With a small core being all that remains from Deus, Murmur proclaims herself his successor until his death and the end of the world on July 28th. Yuno reminds Yuki about her diary's prediction that they will "become one" on that day. As the days pass, Yuki eventually admits to himself that his friends were probably telling the truth. Since he can't understand why Yuno would lie to him, he decides to get the truth from her by fulfilling her diary's prediction earlier. On July 27th, Yuki and Yuno make love, "becoming one". Afterward, Yuki asks Yuno why she lied about resurrecting people being possible. Yuno says that she just wanted to console him and asks him to kill her. Yuki refuses and instead suggests that they die together. When he mentions Aru's message, which claimed that this universe is a second iteration of a world in which Yuno became a goddess and travelled back in time, Yuno attacks him. As he runs away, Yuki is intercepted by Murmur, who shows him visions of the past. Murmur confirms that Yuno has indeed played the survival game once before. In the "first world", where she and Yuki also ended up as the last contestants, both agreed to commit suicide rather than having to kill the other. However, Yuno only pretended to kill herself, thinking she could bring Yuki back as a goddess. When she discovered she could not restore souls, Yuno, wishing to see Yuki again, travelled back in time and killed her other self, taking her place. Distraught at the death of the second Yuno, Yuki breaks out of the vision and confronts Yuno.