Yami Yugi Personality: In the early manga, Dark Yugi starts out as an merciless vigilante. He emerges to deal justice to people who trespass the souls of Yugi and his friends. Although his acts are righteous, he lives up to his namesake of Dark; his Penalty Game punishments are usually very brutal. Later, while living inside Yugi's body, he seems to become more of a caring, nice and friendly disposition, even though he always had that in him, and the friendship of Yugi's friends had helped it be revealed to others. Yami is a strong, powerful and skilled Pharaoh. He attempts to balance darkness and evil in his use of the Shadow Magic from his Millennium Item. Unlike Yami Bakura and Yami Marik, he never uses it for personal gain, instead preferring to help others in need, and to inflict punishment only on people who have severely wronged innocents.

He is slightly reserved, as he doesn't reveal his existence to Yugi or his friends. At first Yugi feared Yami Yugi, but after Yugi admits to thinking "another Yugi" exists inside him, his friends become aware of his existence and accepted him as a friend. Even before, Yami is extremely protective of Yugi.

Yami's pride is his greatest strength and weakness. Initially he refuses to lose games, without considering the consequences. This has caused him to almost kill Seto Kaiba by attacking his monster while he stood on a ledge and the shockwaves could cause him to fall if Yugi chose to win the Duel (in the Japanese version, Kaiba threatened to commit suicide should he lose). Yugi holds him back from such acts at times, but he is not always successful. Yugi becomes afraid to let Yami out for a while, because of the harm he could cause. During his Duel with Rafael, Yami, albeit with great hesitation, eventually ignored Yugi's objections and used the Seal of Orichalcos rather than lose. Ironically, it was this action and Yami's subsequent corrupt actions during the Duel would lead to one of his few defeats and the capture of Yugi's soul by Dartz. Yami expressed great grief and guilt following the battle due to Yugi's willingly suffering, which were because of Yami's actions. However, he was able to conquer and purge the darkness within himself; which also eradicating the malignant influence of the Orichalcos that remains within him. Learning how to lose became an essential aspect of Yami's journey, which he is tested in the Ceremonial Battle.

Yami is also wise and intelligent. He knows all the rules and details of how the game is played, as well as those of all games. He also knows several special game techniques, such as the Double Hit dice roll technique, which, when two dice are used and the one with the weak spin stops first, lets him make the dice that's already spinning hit the one that isn't, allowing him to change its number, which is done by bumping the field with a body part, e.g the elbow.

Despite being an ancient pharaoh, Yami is very quick to learning and utilizing modern technology. He, despite initial shock, was able to quickly grasp the concept of holographic technology, how Dueling Arenas and field Power Bonuses worked, was able to use the Dungeon Dice Monsters Help computer to quickly formulate strategies, and was able to use Duel Disks flawlessly on the first try. Yami is also capable of translating the hieroglyphics of the Egyptians, figuring out the riddles or clues and what they mean.

Through Yugi and his friends, Yami Yugi learns the values and powers of friendship and unity. After seeing Yugi overcome Marik in his Duel with Joey, who has been possessed, Yami thinks to himself, he learned something from Yugi; that in kindness lies the greatest strength of all; one day Yugi will surpass him in every way.[2]

In the Japanese anime, Yami often refers to Yugi as "aibou" ("partner"). There have been instances where he also refers to Yugi as "other me". Being more prideful than Yugi, he uses "ore". As such, he would call Yugi "mou hitori no ore".

Yugi Muto Personality: Yugi is kind-hearted and child-like. He is good at games, riddles, and puzzles, especially Duel Monsters. As Shadi stated when he looked into Yugi's Soul Room, he has no malice or wickedness in his heart.[9] This doesn't mean he cannot get angry at someone, but is willing to forgive them.

Yugi is also very shy when comes to meeting people who admire him, especially girls. As seen with the cases of Mai, Vivian, and later Rebecca, he would often blush and even freeze up when they approached him. Yugi is also not good in front of big crowds, as seen when Mokuba tried to get him up on stage to give a speech.

Unlike his other self, Yugi has no problem with losing. In fact, he is willing to lose if it means helping his opponent. Yugi also has a lack of confidence in his own abilities, but still wants help out his friends. Over the course of the series, he becomes more confident and determined. He is also willing to sacrifice himself if it means saving someone else, such as Joey or Yami Yugi.[10][11]