Her diary is the Yukiteru Diary, which tells her everything about Yuki in intervals of 10 minutes. While this means that her diary is basically useless by itself, if combined with Yuki's Random Diary that predicts Yuki's surroundings, it can cover Yuno's weakness and protect Yuki, making the two a fearsome duo. Even while the diary does not help her much by itself, Yuno can more than enough make for it with her great and cunning intelligence, which has saved both Yuki and herself in several times. She makes up most of the plans the duo uses to save themselves from the attack of the other participants, as well as quickly determinate the weaknesses of certain diary users, like The Twelfth's blindness, or discover that The Sixth's followers were pretending to be dead to ambush them. She is also skilled in traps, seen when she booby trapped an abandoned hotel with multiple tools (this is best seen in the anime), such as electronic locks, concrete (gas in the anime) and even a sickle from an elevator (also in the anime). Her intelligence being her greatest asset.
Yuno is shown to be quite resourceful, using a shard of glass as a mirror to check the position of Minene Uryu during her bombing attack, as well as a pair of stones against The Twelfth to discover him amongst his copycats.
Her perhaps most fearsome ability along with her great intelligence is her near mastery of basically all type of weaponry, mostly bladed, such as knives and axes, and during the attacks against The Eighth and The Eleventh, to be a skilled swords-woman, and using firearms such as a pistol and a machine gun with lethal proficiency. It is believed that she carries around a S&W Special Forces M9 Bayonet as her personal knife. She also is fairly acknowledgable of poison and drugs although she uses them in few times. She has also demonstrated to be quite skilled in infiltration, as she has in more than one occasion enter a building unnoticed even while protected by the police.
Also despite her feminine appearance, Yuno has demonstrated impressive feats of physical strength mostly when angered, seen when she could free herself from two boys her age holding her in both arms, as well as free herself from two Omekata Cult members even when The Sixth kissed Yuki and killed them two, even though she was severely weakened by the excessive amount of physical activity performed at that time. Also during the second attack against The Eleventh she was capable of vertically slicing up a person in half with a katana.
All in all, those who have ever faced and lived to tell the tale, have acknowledged her as a fearsome opponent and can be considered one of the most powerful participants.Tutorials: