Mokuba Kaiba was Seto Kaiba's faithful younger brother. Mokuba loved Seto and supported him no matter what. Mokuba challenged anyone who spoke ill of his big brother. However, Mokuba wasn't afraid to question Seto when he felt that Seto was doing something wrong. When Seto was young and living at the orphanage, he learned that life was tough. Despite their hardships, Mokuba and Seto were able to cheer each other up. However, after taking over Kaiba Corp, Seto's smile faded because he had to be serious and ruthless to stay on top. Mokuba wanted to see his brother smile again.