The main male protagonist of the series and the First Diary user. Also known as Yuki, he is a 14 year old middle schooler who is a rather quiet boy with an anti-social behavior who doesn't talk much. He mostly sees things around him as a bystander and writes it down in his cell phone diary. Yuki becomes involved in the Diary Game when to his shock that Deus, a god-like being whom he thought was an imaginary friend turns out to be real, selects him as one of twelve contestants in a 90 day battle royale where they must kill each other using their special diaries where the last survivor becomes Deus' new heir. Yuki's diary is called the Random Diary, which written from his point of view, gives a detail explanation of his surroundings very accurately whether it be the present or the future. While versatile in any situation, the main disadvantage of the Random Diary is that it doesn't tells him what is happening to himself which leaves him vulnerable. Furthermore, since the diary is written from his point of view, Yuki can be tricked into thinking something he sees is true without realizing it which is a disadvantage for other people who use the Random Diary.