Xiayu (ジウユー Jiuyū?, September) is a member of the Dolls who was kidnapped and brainwashed by Shadaloo to be trained as an assassin working for M. Bison. Her name is derived from the Chinese word for September, Jiǔ yuè (九月, lit. Ninth Month).
Originally from China, Xiayu specializes in using nunchaku.
She has short black hair and dark brown eyes. In Street Fighter V, she starts wearing Chinese Opera makeup to frighten her enemies. Her hair now seems to be stylized in a different way, more pointy than before. She is wearing a navy blue sleeveless dress similar to a qipao and is tied in a red obi, blue stockings and black shoes.
She's gentle with friends, but ruthless with enemies. Normally calm and collected, she'll do anything for her friends when needed. She's very friendly with her twin sister Jianyu. She loves spicy food, steamed dumplings and kung-fu movies, and hates people who badmouth others.
She is a monster with nunchakus. To overcome an enemy, she won't hesitate to resort to surprise and sneak attacks.
Xiayu has never been playable in any of the Street Fighter games, so little is known about her own backstory. So far she has been seen briefly at the end of the Street Fighter Alpha 3 sub-boss scene along with the other dolls. In Street Fighter V, she seems to appear in some characters' story mode, but little is known so far about her role.
Her role in A Shadow Falls is minimal. She is seen accompanying other dolls at various times, but is only seen fighting once; joining many of the other Dolls, she ambushes Cammy and Decapre once their Psycho Power is strengthened by F.A.N.G, but all of the dolls are defeated soundly by the pair. She is seen again at the end, when her along all the other dolls are no longer under the influence of Psycho Power.
In the UDON comics, she was sent from Shadaloo to run the Triad compoud along with Jianyu, where illegal tournaments would occur with fighters from all over the world, which would finance Shadaloo's black market trade and organized crime. Fei Long got caught up in their schemes and turned down a criminal movie offer, and eventually he would join Gen and Chun-Li to take down the Triad by fighting off a legion of thugs and criminals along with Xiayu and Jianyu.
- Xiayu is the only known Street Fighter character whose name begins with an X.