Shizuka Katsuya/Serenity Wheeler is Jou's/ Joey's younger sister. The two share a very close connection. She really isn't in the second season much, but she is in the third a whole bunch. Her eyes are bad, and she needed an eye operation to fix it. It was payed for by Yugi, who donated his winnings from Pegasus' tournament to the cause. She refused to have the operation until her brother showed up at the hospital, but he was held back by thugs. That episode really ,showed how close the two really are. One of my favorite characters, my netname is not based on her, however. The name is the same as an old friend of the family. Only after I adopted the name, did I find out how we are alike. I'm keeping the name.
Isis/Ishizu Ishtar is Malik's/ Marik's older sister, and the owner of the necklace/(What is it in Japanese?)She is really cool. And smart. I think she ownes the Egyptian Exhibit in a very prestigous(sp?)museum. She also might be the best female duelist in the series. (Anzu/Tea sucks)She is trying to keep Malik on track, but his defiance has gone too far for even his own sister to help guide him.
Ryouta Kajiki/Mako Tsunami is an expert water duelist. He is in both the second, and the third season, but not for very long. In the second season, Yugi beat him, kicking him out of Pegasus' tournament. In the third, Joey/Jou beat him, and kicked him out of Seto Kaiba's tournament. He is looking for his father who was lost at sea years ago, but this dude knows he lives. He duels in his father's honor, and to win money for his own ship, so he can keep searching.
Miho Nozaka was never introduced to America, so she has no English name. She is like one of my close friends. She is kinda boy mad. Honda/Tristan liked her, but she did not share the same feelings toward him. She fell for Ryou Bakura, though. Again, she appeared only in the first season that was never released to America.
Mokuba Kaiba is Seto Kaiba's brother. If you looked at the two, you would never think they were brothers, they are so different. Even so, Seto and him shares an unbreakable bond, because they have been looking out for each other for all thier lives. Thier father died in an accident, and his mother died giving birth to him. Ever since then, Seto has always kept an eye out for his brother.
Noah Kaiba is Seto and Mokuba's "evil" step brother, the real son of Gozaburo, who adopted the Kaiba brothers when they were orphaned. This guy lookes a heck of a lot like Seto, but he is much worse. He is trying to take control of Kaiba Corp.