VicePresidentCeo

At the beginning of the manga, Mokuba is very mean and will go as far as trying to trick Yugi Mutou to get back at him for defeating his older brother, Seto Kaiba. Mokuba is a gamer who specializes in Capsule Monster Chess (Capmon), but is not as good of a gamer as his brother. He is so committed to avenging his brother's humiliation, he uses several extreme measures, such as having his friends brandish a machine gun, a knife, and a stun gun in one manga chapter to coerce Yugi to play Capsule Monster Chess with him.
In the Yu-Gi-Oh! Duel Monsters anime, Mokuba is eternally devoted to his brother Seto Kaiba and is constantly by his side. He is more naive and good-natured, and will do whatever his brother tells him to. He also seems to trust Yugi and his friends more than he did previously. There is a part in one episode when he saw (Yami) Yugi watching him from another building when he was about to kick some brothers out of the Battle City grounds, when he considered, "You know, I bet Yugi would give them another chance!" He must really respect Yugi as he starts to think like him.