|Family||Parents (divorced), Jounouchi Katsuya (older brother)||Occupation||Student
Kawai Shizuka (Serenity Wheeler in the dub), is a minor character in the series, so not much is known about her. She is the delicate, shy younger sister of Jounouchi, and tags along with the gang on their Battle City journey.
Not much is known about Shizuka's childhood, except that she is really close with her older brother, Jounouchi. When they were still kids, their parents divorced, and the siblings were also separated - Shizuka went with her mom, and Jounouchi with his dad. It was a tearful experience for both - and they haven't seen each other since.
Before the Duelist Kingdom tournament, Jounouchi receives a message from Shizuka, telling him that her eyes were gradually failing and that she would go blind soon. So Jounouchi decided to enter the Duelist Kingdom tournament with Yugi, hoping to win the $3 million cash prize to pay for his sister's operation. He ended up losing to Yami in the semi-finals, but he let Jounouchi take the cash prize because he knew that he needed it to help Shizuka.
With her brother's support, she goes through with the operation, and it was a success. After she recovers, Honda brings her to the Battle City tournament so that she could watch and support her brother in his duels.
Shizuka is also quite popular with the boys. She has Honda and Otogi both fighting for her affection, much to her brother's annoyance. However, she seems to have no interest in them.
Shizuka and Jounouchi share a special bond, and they are always looking out for the other. Since Jounouchi is a couple years older than her, he is very protective over Shizuka, and she looks up to him so much. It seems nothing can ever break their bond.