She was a stalker of Masanobu. She died after being hit by a truck driver who fell asleep. Her nickname given by Gantz, "Sadako," is due to her bearing an extremely uncanny and creepy resemblance to the homicidal "ghost" Sadako in the Japanese "Ringu" horror novels and movies.  (Source: Wikipedia)

Tokyo teens Kei and Masaru are killed by a subway train but awaken in a room with an ominous black orb that gives them weapons, suits and orders. Fighting bizarre alien monstrosities in a deadly game, will they win their freedom or die for the final time? 
(Source: Dark Horse)

Thought your life was bad? Sometimes, death is worse. There is no salvation, peace, nor god waiting to receive you into their care. But wait, a god? Maybe you are talking about that big black ball stuck in the room with you. Now you are thrown into a game, fighting green aliens and robot monsters for the chance to survive. 
When Kei Kurono is killed, he thus finds himself caught in such a game; a test of his skills, morals and will to survive. His life is not his own, his death spat and trampled upon over and over again. What happens if he does not listen? God knows. 
A word of warning: Gantz is not for the faint-hearted, but neither is it as simple as it looks. Gore, rape and violence is rampant, as are portrayals of greed, violence, and all the ugliness that one sees in society today. 
[Written by MAL Rewrite]

__Non-Anime Roles:__
- Kula Diamond in _King of Fighters_ game series

Kurono Kei and his ex-elementary school classmate, Kato Masaru have survived the first two ordeals that the unknown black sphere Gantz has sent them through. Exploding body parts, struggling to stay alive till the last seconds and seeing your fellow comrades fall in a pile of blood and gore are norm to them now. They are aware now that Gantz can call them up along with any new deeds, at any time for another confrontation with aliens. 
Will Kato's experiences in the Gantz world give him the same courage in the real world? With fellow veteran Gantzer Kei Kishimoto currently staying at Kurono's home as his "adopted pet", can Kurono stave off his growing lust for her mammaries? 
What the heck is Gantz? 
(Source: anime-source.com)

Sadayo Suzumura