Shizuka Kawai (also known as Serenity Wheeler in the 4Kids dub) is a character from Yu-Gi-Oh! She is the little sister of Joey Wheeler. At a young age, their parents divorced and they were separated; Shizuka lives with their mother, while Jonouchi likely stays with their father. She has had bad eyes since she was born. At the beginning of the series, she nearly goes blind and Joey tries to pay for her operation to save her from that fate. Eventually, she is given the money by her brother with the operation for her eyes being a success. She would later accompanies Jonouchi and Yugi, along with their friends during the event of Battle City and the Virtual World, and becomes the romantic interest of both Hiroto Honda and Ryuji Otogi. It is hinted from Otogi after the KC Grand Championship that she and Jonouchi have started and are finally living together again.
Like her brother, she is also an amateur duelist when she used weak monsters and doesn't know how to summon monster in position.
She was voiced by Mika Sakenobe in the Japanese version and Lisa Ortiz and Alison Lester in the English version.
Shizuka's character design was overseen by Kazuki Takahashi. In the second series anime, Shizuka wears light blue denim shorts and long white socks with blue sneakers. Her top is a sleeveless pink and white shirt with a high collar that is worn on top of a short-sleeved yellow shirt. She does not change this outfit throughout the series except when she is in the hospital, where she wears simple pink pajamas. The photo that Katsuya Jonouchi has of her in his wallet shows her dressed in a sailor fuku common to middle school students in Japan. In the Japanese version of the final episode's end credits, she wears a white shirt with some pink linings around the edge of its collar, sleeves and bottom, and a orange short skirt. In the manga, she wears longer sleeves and jeans rather than the shorter clothes that she wears in the anime. In the first anime series, she has lilac hair, but it is light brown in the second series. She has green/brown eyes.
Shizuka is a gentle-natured and compassionate girl who is rather dependent on her friends and seems to be generally more timid than the other females. She is also shown to be extremely trusting to the point of naivety, believing Honda when he says, in an attempt to impress her during her recovery from her operation, that he taught Jonouchi everything he knows about Duel Monsters. However Serenity has shown to have her own inner strength, such as when she took off her bandages to see for the first time, to save Jonouchi by diving into the water. Serenity also after an inward struggle of self blame, was the key to defeating Soichiro Ota and she pulled through.
Optimism seems to be one of her key features, which one would need to survive nearly going blind, being aware she may not get the operation. Prior to Duelist Kingdom, Shizuka was separated from her older brother Jonouchi to live with their mother when their parents divorced, but they seemed to have kept in contact over the years, as Serenity looks up to him and they both love each other dearly; during Duelist Kingdom, Jonouchi is seen to have a picture of her in his wallet. Jonouchi often states that Serenity was his biggest inspiration throughout Duelist Kingdom and Battle City. She shares a strong bond with Anzu Mazaki and Mai Kujaku, and Anzu even takes her sightseeing at one point.
Shizuka's character is portrayed as a very beautiful young girl, capturing the romantic interests of both Honda and Otogi. This leads them to constantly argue over her during the Battle City arc and both eventually end up giving her their number. It is never shown if she ever liked either of them as more than friends, though she is always amused at their antics and even looks relieved at one point where Honda drags Otogi away from her. But she did seem to be more fond of Honda than of Otogi.
Her innocent nature was even able to make one as self-centered as Seto Kaiba be considerate enough to get medical help for Bakura even during the Battle City Tournament.