|Novel||Itachi Shinden: Book of Bright Light|
During the finals of the Chūnin Exams, Nemui was pitted against Itachi Uchiha in the semi-final round. His fighting style gave Itachi trouble, as it allowed him to dodge his attacks and made genjutsu ineffective. Eventually, Itachi found an opening in which to cast genjutsu on Nemui. After using genjutsu during each opening, Nemui becomes too traumatised to continue the match, granting Itachi a victory.
True to his personality and nickname, he is presumed a lazy shinobi, or just a sleepy-head. However, he is also cowardly in nature, and that fear renders him unable to fight effectively while awake.
Nemui's core skill is his ability to fight while sleeping. In order to fight effectively, Nemui intentionally falls asleep during battle. While asleep, he is able to fight with such proficiency that even Itachi Uchiha had difficulty keeping up with him. Also, he is immune to any jutsu involving eye contact, such as Sharingan-based genjutsu. Nemui's fighting style has one major weakness: he must wake up periodically to maintain awareness of the battle. During those periods, opponents have an opening to attack.
- "Nemui" (眠い) means "sleepy" or "drowsy", alluding to his fighting style and nickname.