Sumiko Yamada is Miho's friend and member of the Osaka Team.
Sumiko is a gantzer from the Osaka Team that participated in previous Gantz Missions along with her friend Miho.
Sumiko Yamada is a supporting character from the anime/manga series Gantz, created by Hiroya Oku. Though the Osaka Team appeared in chapter 241, Sumiko wasn't introduced until Gantz Volume 22, CH. 252 "The People from the West". She didn't appear in the anime version.
In GANTZ/ OSAKA, Special 2, Sumiko along with Miho, Kuwabara and the boy with glasses are seen in the Black Sphere's Room after the Nurarihyon Mission. Everyone except for the boy with glasses gained enough points to access the 100 pts menu so they decided to leave Gantz. Miho left because she thought there was no point in staying in Gantz without her boyfriend Nobu, and Sumiko left because she didn't want to continue without Miho.