The Future Diary - Season 1 Episode 18 Crossed Lines

In a flashback, Yuno is revealed to have murdered her parents, who used to discipline her harshly for failing to meet their standards. After she fell in love with Yuki, he became her sole reason to live. Yuki asks Deus to bring his mother back to life, but he reveals that he is dying and his powers have faded. Furthermore, unless a successor is determined soon, all existence will collapse. When Yuki's father returns home, Yuki, who knows he killed his mother from his diary, demands that he turn himself in. However, his father points out that he has no evidence. The next day, Yuki goes after his father, expecting him to lead him to evidence. However, it turns out that Yuki's father wanted to visit the site where his family was going to go stargazing before he turned himself in. As Yuki reconciles with his father, they are ambushed by agents of Eleventh and Yuki's father is murdered. Enraged, Yuki fights back and manages, with Yuno's help, to kill the attackers. Afterwards, Yuki declares that he is now determined to win the survival game in order to attain the power to resurrect his parents. When he tells Yuno this means he has to kill her, she calmly replies that she is ready to die for him at any time.